no power past half throttle

[Mitternacht]

I just recently changed my 98 GT from a supercharged setup back to stock. Car runs fine, idles fine, drives fine, but after half pedal it loses power. Recently changed spark plugs and wires, IAC, and the module that controls the EGR valve. No vacuum leaks. Cats not glowing. Pulled the Diablo chip out of the computer. Car still has Walboro 255. Other than falling on its face from half pedal on, the car runs great. When I try to run past half pedal, exhaust has a weird smell and code scanner keeps saying right and left banks running lean.

Is the tune still in the stock computer? What else could cause this?

[White5.0]

probably just not used to the stock power after taking the supercharger off lol

[no1sirbutler]

if you physically pulled a chip out of the comp then its running on the stock tune. is your fuel pressure set properly esp since your running the 255?

[Mitternacht]

Its not that. After about 3500-4000 RPM's, theres no power at all.

[Mitternacht]

if you physically pulled a chip out of the comp then its running on the stock tune. is your fuel pressure set properly esp since your running the 255?

That I'm not sure of.

[no1sirbutler]

that could be your problem. the stock comp may not be able to run the 255 properly. im not sure but if your running lean then maybe its not upping the fuel pressure enough at those rpm levels

[INSANELY CRAZY]

size injectors? maybe your dumping too much fuel not enough air ratio.

[Mitternacht]

size injectors? maybe your dumping too much fuel not enough air ratio.

The injectors are stock, but I still have the Walboro 255.

[John4cam]

Try cleaning the maf wire with some contact cleaner. Did you put the stock maf back on??

[ModularMike]

probably just not used to the stock power after taking the supercharger off lol

LMFAO that made my day!

[RUTHLESS]

I am not 100% sure if this will work for you but on my 98 F150 I have to pull the batt to reset the computer when I change tunes.

What do the plugs look like? Do they look lean or rich?

BTW this might sound strange but back when I had my Sealth TT I had an issue that caused the car to run so rich that the ECU kicked of a lean code because the gas wasn't burning. I know that sounds messed up but it happened to me and the stupid ECU had me looking for a lean code when it was rich as all hell.