going lean
 

Okay, my fuel pressure is good, new fuel filter and my car goes lean at around 6000 rpm in 4th gear. Can anybody tell me why?

all I have is a k&n filter, downpipe and catback.

i've been researching downpipes - and what happens after you add one - for a while now, and i've often read that adding one can cause you to run lean. there's all kinds of contradicting theories on that, though....

dont think that its the down pipe for it doesnt go lean in 1st, & 2nd, rarely goes lean in 3rd but always does in 5th. Somebody told me could be because the computer doesnt sense load or something and takes the gas away,
anybody else???

Maybe you want to see if the engine has any code? I've heard that the Air Mass Flow sensor goes bad for those people that have K&N or foam filter/intake.

Also, is your injector in good shape? Any intake manifold leak?

I'm not getting a light so I think that rules out a code and it only does it around 7psi, doesnt go lean at 10psi.

Sometimes the check eng light only flashes briefly and goes away. It's 5 min to ground the GND and TEN terminal on your diagnostic port. It's a good idea to read the code once in a while anyways.

I checked it, there is no code, any other opinions????