Issues on a 2017 Tiguan

Hey there. I have a 2017 Volkswagen Tiguan Limited and I love this car I just hit the 80,000 mile Mark threshold and I had to change my battery and so when I did I had a bunch of problems come up after the battery changed I did the battery reset I've changed out the PCV valve I've changed spark plugs I've changed high pressure fuel pump I've changed cam follower, also did my MAF as these are things that were recommended to me by a mechanic and I'm still having issues with certain things. The symptoms include mildly sluggish acceleration and at cold start the car starts normally but then immediately tries to die and either fully dies or will cook into its normal idle. One more issue I've been noticing is at running temperature there's a loud groan coming from the engine bay when I accelerate only. There are no codes coming up at all, the last code i had was a year ago and it involved the Cam Sensor and i did that no problem. Has anyone experienced these issues and what did you do to fix it? VW service techs gave me 0 info and just kept telling me to bring it for a 250 buck diagnostic....

Thank you for reading and possibly giving me information 😭