I swapped my sons engine with an engine I got off eBay. What was supposed to be a Camaro engine turned out to be a traverse engine. I still did the swap because my son was moving out of state. Swap went good, drove it about a 100 miles and things started to happen. First code was the misfire on all cylinders P0300-P0306. Car sat for a week, started it up and ran perfect.Put 50 miles on it and it through a Cat code. Then a couple days later P0300-301-303-305. Replaced ignition coils, purge valve, crank shaft and cam shaft position sensors. Chased it down to the ECM. Bought a new ECM and took it to a speed shop to get it flashed/ programmed/ and updated. Didn’t work! I know I should’ve just sent the engine back but I’m in to deep now. I’m at the end of my knowledge and I’m just praying that someone on this forum has had or knows someone that had this problem and actually figured it out. Oh and I actually tried to clone the ECM too. My only other thought is to buy a traverse ECM and put that in there and try it. Please help and thank you in advance!