I have had my 2003 Impala Base 3.4L for about a month now, and got the Intake done a couple weeks ago. My check engine light has been on since I got it (had scanned and is a bad egr), but it has been doing great on gas until this week (I would guess I have driven 60 miles and used 1/3 tank of gas!), but a tank has been lasting 2 weeks up until now) I have noticed a pretty major loss of power since the intake was done (maybe related, maybe not), but it has been running fine. I have also noticed it seems to hesitate when it shifts, especially when it is cold. The rpms seem to get higher than normal, and it kind of hesitates into the next gear. The most noticeable is from 1st to 2nd. (it could just be me though, my last car jerked hard into every gear, this one is still much smoother) I am wondering if the egr is causing all of this, or if something else is up. (I don't know if this is related either, but for a few days after the intake was done, the exhaust looked somewhat smoky/hazy and had a really strong, lingering chemical odor, something like bleach or fertilizer. It went away though.) It has a new oil pressure sensor (a few days after the intake gaskets), new valve cover gaskets, and resonator removed (catalytic converter is still in place though) The car has 163,000 miles. Currently not leaking or burning any fluids.