2012 Camaro LFX with stock internals, just bolt ons. The engine is a replacement from a 2015 with 7k miles on it installed 2 months ago. Never had the issue with the original motor. The car randomly will fluctuate timing/TPS readings at idle. The logging looks like a heartbeat. Timing will vary from -3 up to +25 degrees and TPS 1.6 up to 4%, then repeats. It doesn't do this every time i stop, but a lot of the time which makes it harder to diagnose. So far i have replaced the intake and TB gaskets, MAF sensor, Purge Solenoid, Brake booster check valve, and the hoses to my catch can. Car drives good and ltft while driving are +/- 3%. Any ideas?