I hooked up an aftermarket tach to the wrong side of my coil and fried my ECM somehow. If I had known that was the problem I would have got a new used ECM at a yard, but I threw in the towel and had a mechanic diagnose the problem. They said a new aftermarket one was like 150, so I just said do it.

I would not start replacing ECMs until you know exactly what's wrong, seems like you don't know for sure but you just have a feeling.

I've had exhaust shops weld on my truck a number of times and no problems.

Although, I have also gone through 4 computers. When I bought the truck it had a 92 Astrovan ECM in it. Then before I knew anything about engines, I had a mechanic replace my oil pan. He pulled the motor, replaced the pan, but when he put everything back together it wouldn't start. He said my ECM was bad and charged me $80 for a used one. That was a 92 Rodeo ECM.

I fried that as mentioned above, and now I run the aftermarket refurbished one.