Hello! I’ve been running into a weird issue with my new to me 89 camaro. Normally it will slightly hesitate however, after about 15 to 20 minutes, it loses half its power and the check engine light comes on, and it will backfire out of the exhaust. It has a lot of new parts/sensors like spark plugs, plug wires, IAC, ignition coil and ignition module. I ran the codes and got codes 10, 35, 44, 55. I am thinking it may be an ECM due to all of these popping up at once and one of them being a code for ECM issues.
I checked the timing and base timing was at 0° however when I hooked up the ECM, it advanced way out of the scale to the point I could not see it from the top.
This is my first order car so I apologize for my lack of knowledge, but any advice is greatly appreciated!

 

Check for loose ground wire connections and broken wires-those can set odd codes.Also remove and reinstall all the fuses in the fuse panel one by one to re-establish connection.

 

Not sure I've ever come across a code 10 or a 35. Are those correct?

44 is an O2 sensor (low voltage or lean exhaust)
55 is an ECM error

I'd start with the obvious things first. I'd see if the O2 sensor is still connected. Perhaps the issue is occurring once the ECM changes from Open to Closed loop where it takes into account O2 reading to adjust fuel trims (BLM and INT). With a faulty O2 signal it could be affecting the fuel supply and thus once it warms up with a backfire.

As for timing it sounds like you're setting base time with the EST wire pulled? If not be sure to. I run about 6 degrees advanced with base timing.

I see that you replaced your ignition module. What did you replace it with? I've heard aftermarket out of the box can be stubborn. Also, with heat soak maybe being an issue I'm assuming the distributor base plate was cleaned and fresh thermal paste was applied? ICM's are heat sensitive and thus need this paste for effective conductive heat removal.