I just finished installing my headers. I used te EGR hook up since my headers has it. It is a new egr valve and it keeps throwing a code P0400,
How could the egr be bad, it is a brand new GM one. Also the hook up is thight to the headers and the plug is connected to the EGR valve.
What is going on?

There is not enough backpressure for it to work properly. Either learn to live with the code, or get it programmed out. I had the same problem

before headers. it had the borla on it. Dealer put on new valve, sloenoid and vacuum lines under warranty to no avail and finally diagnosed it as non OEM exhaust. I just clear the code and go on my way. You'll know when the egr is bad.

I randomly get Code 32 EGR System Fault. I'll just be driving and my check engine light will come on. Happens a couple times a month.

Car is completely stock. Would this actually be causing a problem, and if so, what?

Thanks.

For OBDII if you have to pass an emissions scan you can look up a thread in the computer/diagnistics section I started called fooling the pcm to have the egr monitor ready. There's a few ways there to fix this problem.
If you don't have to pass emissions you can have the code edited out or even pull out the dash and block the SES light with a piece of cardboard like I did for a year until I finally had to pass the OBDII for the first time here in 5 years.
Can't give any advice about OBDI.

Thanks guys for your help.
So this code or th eegr not opening, does that affect th proformance at all?

Your egr is still functioning, it is just not seeing the proper flow.

When you edit your PCM all you are removing is the DTC. The funtion is still there and the computer is still telling it to work. You are just turning off the SES light if it doenst work correctly.