Fitted a genuine CTS. Car temp now registers properly on Gauge and climate. But any throttle over 2k rpm and the car loses alot of power and backfires!!!

Next step i guess would be to put my old throttle body back on! But i manage to lose my 5mm socket allen bit. gone down the back of the engine with no where to be seen now.

Think im gonna give the car a valet and stick it up for sale, the bag of sh*t