Burying money looking

What engine did you install? Did you use the Caddy ECU?

3.6. No he used the camaro ecu.

Car ran great for about 500 miles. Timing chain stretched on old motor and cracked three rocker arms. Needed new motor.

Maybe the Cadillac ECU would fix things but as you first said there may be a transmission incompatibility issue too. Obviously your mechanic needs to check out the engine for problems. I doubt you will ever get it completely sorted out which is why I always discourage people from swaps like this.

The car ran great on which engine? If the new engine ran good for a time then you need to check out the engine and I would check the catalytic converters in case they are plugged.

I did get an o2 sensor code and it misfire the right side of motor. 2 4 6. Plus that exhaust pipe runs hotter.

I'm a lil car savvy but this has me baffled.

It ran great on the new motor but had a slight jerk when u took ur foot off gas. I had work done in ga and needed to get back to st louis. So I took off within hours of having car completed.

I have even changed high pressure fuel pump and all injectors.

Do a back pressure test on the cats and make sure you fix the misfire.

Dealer tells me left cat is clogged. What would cause black tar substance to pour out exhaust pipes?