Still poor perfromance one thing leads to another

[rearviewsg]

I have a 94 explorer xlt
and i am having some trouble. I was getting a low voltage mass air flow sensor engine code. I cleaned the air flow sensor and replaced. It didn't do any good. I replaced the MAS and it worked great for about 10 miles and now I'm still having the same problem. It feels like it is loading up while operating on the bottom end at about 30-35 mph or 1200-2200 RPM, almost like it is missing.
i also checked my fuel pressure and it was so psi at an idle and when you pull the vacume hose off of the fuel pressure regulator and the pressure rises up to 39 psi at an idle.
i checked my codes again and i was geting a high exause pressure code but that can't be possible because i basicly have free flowing exaust i have no cat and a 3 chamber flowmaster so there isn't to much restriction
one thing i have noticed is there is a propane smell and i have no clue what that might be.
Any ideas? thanks
Dustin

 

[410Fortune]

Sounds to me like you have too much flow in your exhaust.

You see your 4.0L needs some backpressure, and it also relys HEAVILY on the reading it gets from the 02 sensors.

So removing your cat could be part of your problem.

How did you remove the cat? did you just gut it? = bad idea. If one was to eliminate the cat coverter from their 4.0L (WHo would that is illegal) the proper way to do it to keep from creating an expansion chamber that will actually slow the exhaust flow down, is to run a pipe through the cat.

When did your problems start (modifications you made)?
What codes are you getting now?

the first code that comes up is the one you want to start with, all others after it may be related.

 

[rearviewsg]

I cut my cat off like a year ago and what i did is i cut the ends off and welded a pice of pipe inbetween thee ends the pipe is the sale size as the stock exaust and i had no problems at all others mods are a intake kit which i also did like 8 months ago
i was geting a maf voltage to low code so i tried cleaning it that didn't help so i replaced it
i was also getign a thrtle higher than expected code.
and a high exaust pressure code.
no o2 sensor codes or anything.

Thanks
Dustin