2003 4.6L has a bad idle and barely enough power to crawl down the street. - Fuel pressure is 65 PSI - Tested several injectors and got 12-14 ohms - Tested several coils and got resistance across the terminals of about 0.5 ohms - Tested the TPS and it seems to be fine - Tested the MAF based on a thread from 2000StreetRod. The specs don't match, but the existing MAF is comparable to a remanufactured replacement. MAF has been cleaned. - Plugs are brand new NGK iridium and show a light gray color. - No apparent vacuum leaks. Manifold bolts are tight. History: the long block in the truck is new. I replaced it because the old one exhibited the issues I'm seeing now, and I also had bad oil pressure on an aftermarket gauge. Carryover items from the old engine include a Trick Flow intake manifold and throttle body. The combo ran great for about four months prior to drastically losing power. Power output gets worse as the engine reaches operating temp. No overheating. EGR is not currently connected (needs to be modified, as the tube interferes with the upper plenum on the Trick Flow), so I do get a code for that. Feels like it's misfiring but no misfires are being recorded. If I slowly open/close the throttle, it will continue to run, albeit poorly. If I get on and off it fast, it'll rise up and then stall. When I experienced the original issue, it had run great up until it didn't; the loss of power was very sudden. I have codes for the EGR, of course, and also saw some from when I disconnected an injector and a coil to try and trigger a misfire code (which it didn't, oddly enough). I also had codes for primary and secondary fuel pump circuits, which I'm trying to replicate (I started it without the fuel pump relay once, so that may have been the cause). I cleared the codes and am letting it idle now to see what comes up. Additional testing - in park, throttle completely to the floor, I can't get over 1500 RPM.