USAF85

Hello i have a 97 camaro with a lt1 about 105,000 on it it is completely stock. i had a ses light come on and had the car scanned i had the following codes:
p0430,p0400,p0172 and p0175. on the p0400 code i have replaced the EGR and solenoid and the code still came back. on the other codes i am completely lost it idles slightly rough but as soon as i give it a little thottle it runs perfect. if anyone could give me an idea of where to look i would greatly appreciate it. thanks!

Injuneer

P0400 means the PCM cycled the EGR valve and did not see the expected change in manifold absolute pressure (MAP). Since you have replaced the solenoid and the valve, you need to check the vacuum lines to make sure they aren't leaking. And you need to check the opening on the manifold to make sure it's not carboned up. Then check the corrugated riser tube from the passenger side exhaust manifold to make sure it's not cracked or plugged.

If you have headers, or deleted the cats, the EGR flow could be reduced by the lower backpressure in the exhaust system. But you indicate the engine is bone stock.

P0430 - indicates low efficiency on the Bank 2 (passenger side) catalytic converter. Before assuming the problem is the cat, swap the two after-cat O2 sensors side to side. If the problem stays on the passenger side, its a faulty cat. If the code moves to the drivers side with the snesor (P0420) it's a sensor problem.

P0172 and P0175 - indicate that both banks of the engine are running rich, and the long term fuel corrections (LTFT's) are approashing their limits with respect to being able to correct for the rich condition. The LTFT's wil start pulling out fuel in response to rich readings from the pre-cat O2 sensors, but can only subtract about 15% of the fuel before they hit their limit.