tune question on my 01

[bud miller]

after intalling ported exhaust manifolds on my 01-and getting rid of the ol' pup cats..
i know i need a tune..cause the car feels kinda flat between 2-4k rpm..and feels really breathing easy at the higher rpms/
so my question is, does the removal of pup cats and increase flow of the manifolds cause a lean condition?? what does the tune really change or adjust.
thanks for the insight...
bud

[PerforminNorman]

Originally Posted by bud miller

after intalling ported exhaust manifolds on my 01-and getting rid of the ol' pup cats..
i know i need a tune..cause the car feels kinda flat between 2-4k rpm..and feels really breathing easy at the higher rpms/
so my question is, does the removal of pup cats and increase flow of the manifolds cause a lean condition?? what does the tune really change or adjust.
thanks for the insight...
bud

I could be wrong but I think that when you open up the exhaust, it causes the O2 sensors to think it is running lean and thus it throws more fuel at the motor.

I know someone with more knowledge will chime in here if I'm wrong. It happens a lot now that I'm married again.

[FRC Tom]

A less restricted exhaust will flow more air threw the engine causing the afr to be leaner.
Your fuel trims most likely are now on the positive side.
At cruise the pcm will keep you running at 14.6 but when you go into PE (WOT) the pcm will add way too much fuel causing you to go rich.
Adjusting the maf table will fatten her up.