4.0 SOHC, Hard to start, 9mpg, hissing. '03 Eddie B

[SporadicThought]

I'm hearing a hissing under-hood when I let off the throttle. The truck is not wanting to start unless I open the throttle about halfway. MPG went from 15 to 9.
I'm guessing the hissing is a busted vacuum line, not sure where, though. Possibly exhaust leak from not finding that gasket.
Previous to this:
I put new gaskets on the intake. Had to replace the fuel injectors while I was in there (two had some serious melting and deterioration). I bought some cheap ones for $50/6 off eBay.. had some good reviews that weren't obviously fake. The injector seats were ****ed; so those had to be chipped out with simultaneous vacuum to keep the bits from falling in. Cleaned the **** out of everything above the head. I guess there was a sponge-looking deal that came stock (noise dampening); it hard turned into a garden-soil type sludge. Cleaned the MAF with CrC MAF cleaner. Zip-tied the little supplementary box that goes on the air intake hose.
We have 203k. I replaced the gaskets on the oil cooler and oil filter adapter. Had to pull the passenger exhaust manifold to get that done. Replaced exhaust mani-to-block gasket. I did not see one for the pipe end and don't know what it's supposed to look like. I pulled the coolers out and washed them with coil cleaner. New water pump. New belt tensioner and idler pulley. Heater hose 'T' connecter and vacuum-switched inlet valve had disintegrated when they were pushed aside to replace the chain tensioner; replaced that **** with a new valve and t-connector. New coolant reservoir. A few random coolant hoses needed replacement. Recently replaced thermostat housing. Probably something else I'm forgetting.. oh yeah the ****ing EGR pipe was a PiTA to remove, but I finally got it. Put some anti-sieze on both ends on reassembly without knowing if that was a good idea. Trying to troubleshoot the hissing noticing the hissing, and I noticed I hadn't popped the fuel supply line back onto the rail properly. The metal clip was holding it halfway together for about 20 miles. Popped it down with a click and cursed myself for that one. Fuel filter replaced 500 miles ago and I broke one the quick connect clips; so its kinda wedged in there now, but seems secure. Knock sensor is missing all its insulation. Replaced 2 of the rubber/silicon egr vacuum hoses. Dumped a bunch of seafoam high-mileage on the rear timing chain and guide. I swear there was no rattle at all for 100 miles and now it just returned a little bit. I originally drove it for about 6k with progressivly worsening rattle, until the point that it rattled any time motor was under 1k rpm. At first it would only rattle for a few minutes after startup and then clear up. Wish I would have discovered those manual tensioners back then.

I have Forscan and the Short Fuel Trim numbers sit around 10%. At 2k - 3k RPM or so one bank goes -5% the other hits 2%. I think it was the short trim anyway, but now I'm not sure if was long trim. I notice the trim #'s with ODBII in the field are different from the otherwise same-named fields. In the past 20 - 25 starts I got 2 'early misfire / cylinder 2' which cleared out each time and were about a week apart.

So it's a hot mess. I'll tell you this; it runs a hell of a lot better than before I did all this work to it. I also did all the control arms, hubs, bearings tie rods, toe links, sway bushings, etc about 6k ago.
Today, when I put it in drive its a ****inç beast. I'm out here beating the **** out of the mid-sized sedans and such. Oh wait, now there is the bit of roughness and 1 second hesitation /lack of power before the ponies kick in; that was never happening before. Used to startup in like half-second of cranking. Now it is 2-3 bursts and have to work the throttle for a decent start. Even after trying to leave the key turned on for low fuel pressure possibilities.

Any ideas what my order of troubleshooting should look like?

 

[SporadicThought]

I'm hearing a hissing under-hood when I let off the throttle. The truck is not wanting to start unless I open the throttle about halfway. MPG went from 15 to 9.
I'm guessing the hissing is a busted vacuum line, not sure where, though. Possibly exhaust leak from not finding that gasket.
Previous to this:
I put new gaskets on the intake. Had to replace the fuel injectors while I was in there (two had some serious melting and deterioration). I bought some cheap ones for $50/6 off eBay.. had some good reviews that weren't obviously fake. The injector seats were ****ed; so those had to be chipped out with simultaneous vacuum to keep the bits from falling in. Cleaned the **** out of everything above the head. I guess there was a sponge-looking deal that came stock (noise dampening); it hard turned into a garden-soil type sludge. Cleaned the MAF with CrC MAF cleaner. Zip-tied the little supplementary box that goes on the air intake hose.
We have 203k. I replaced the gaskets on the oil cooler and oil filter adapter. Had to pull the passenger exhaust manifold to get that done. Replaced exhaust mani-to-block gasket. I did not see one for the pipe end and don't know what it's supposed to look like. I pulled the coolers out and washed them with coil cleaner. New water pump. New belt tensioner and idler pulley. Heater hose 'T' connecter and vacuum-switched inlet valve had disintegrated when they were pushed aside to replace the chain tensioner; replaced that **** with a new valve and t-connector. New coolant reservoir. A few random coolant hoses needed replacement. Recently replaced thermostat housing. Probably something else I'm forgetting.. oh yeah the ****ing EGR pipe was a PiTA to remove, but I finally got it. Put some anti-sieze on both ends on reassembly without knowing if that was a good idea. Trying to troubleshoot the hissing noticing the hissing, and I noticed I hadn't popped the fuel supply line back onto the rail properly. The metal clip was holding it halfway together for about 20 miles. Popped it down with a click and cursed myself for that one. Fuel filter replaced 500 miles ago and I broke one the quick connect clips; so its kinda wedged in there now, but seems secure. Knock sensor is missing all its insulation. Replaced 2 of the rubber/silicon egr vacuum hoses. Dumped a bunch of seafoam high-mileage on the rear timing chain and guide. I swear there was no rattle at all for 100 miles and now it just returned a little bit. I originally drove it for about 6k with progressivly worsening rattle, until the point that it rattled any time motor was under 1k rpm. At first it would only rattle for a few minutes after startup and then clear up. Wish I would have discovered those manual tensioners back then.

I have Forscan and the Short Fuel Trim numbers sit around 10%. At 2k - 3k RPM or so one bank goes -5% the other hits 2%. I think it was the short trim anyway, but now I'm not sure if was long trim. I notice the trim #'s with ODBII in the field are different from the otherwise same-named fields. In the past 20 - 25 starts I got 2 'early misfire / cylinder 2' which cleared out each time and were about a week apart.

So it's a hot mess. I'll tell you this; it runs a hell of a lot better than before I did all this work to it. I also did all the control arms, hubs, bearings tie rods, toe links, sway bushings, etc about 6k ago.
Today, when I put it in drive its a ****inç beast. I'm out here beating the **** out of the mid-sized sedans and such. Oh wait, now there is the bit of roughness and 1 second hesitation /lack of power before the ponies kick in; that was never happening before. Used to startup in like half-second of cranking. Now it is 2-3 bursts and have to work the throttle for a decent start. Even after trying to leave the key turned on for low fuel pressure possibilities.

Any ideas what my order of troubleshooting should look like?

I noticed the PCV is actually not clipping in. I think it's supposed to turn and actually seat into some type of notch. I think it used to. That notch must have broken and so now it just rotates freely.
I put another small o-ring behind the PCV o-ring so it actually seats in the groove alongside the main o-ring. The PCV now fits into the valve cover very snug.
The hissing seems to have gone.
Still hard to start though.