TBI issues-surging idle

[Greenlee]

I'm just getting this truck back together after a long rebuild. It's an 87' with a rebuilt crate 350. The computer and wire harness are from an 89' Suburban that ran great when I stripped it for parts for this truck. I have headers, a new 3 wire O2 sensor and dual exhaust. All fuel lines, gas tank, fuel pump etc. are new.

Issue: it runs great at start up. Sometimes it continues running great. Other times when it goes into closed loop it starts surging at idle. Sometimes it surges bad enough that it dies. It sometimes dies at stop signs. Other times it runs runs fine.

Over the weekend I got a check engine light shortly after I started it. This doesn't normally happen. I checked the code and got code 54. I have read up on this and code 54 is related to the fuel pump relay. It usually coincides with truck turning over and not starting. I haven't had a problem with it not starting.

Today I drove the truck to work and back a total of about 70 miles. This is the farthest I have ever driven the truck since putting it back together. This time I got a check engine light after driving on the freeway for about 20 minutes. The code this time is 32--EGR. I have been reading up on code 32 and most people don't have the symptoms I have. Some say code 32 can be caused by not having enough back pressure with headers and dual exhaust.

So to make a long story short, I have these random codes that may or may not have anything to do with the truck not wanting to idle after it warms up. Anyone have any ideas where I should start looking first? Thanks in advance for your help!
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