Q: Engine knock noise after changine alternator was replaced

So a while back my car just farted out in the middle of the street, i was confused and could not figure out why, i figured since the car died while it was on it could of been the alternator. I pulled the car over and it wouldent start, i asked a few people and they said it could of been my alternator, so i bought a used alternator took the radiator, fans, car headlights, and everything that comes with it out, replaced the alternator and put everything back together. Car still dident start, changed the battery and then the car started, one problem, theres now an knock noise coming from the engine. when revving its not so apparent but its when the revs fall is when it is. The noises comes in and out bit mostly is there, about a month ago aswell i out non premium gas in thr car when it olny takes premium by accident.

Thanks

My car has 97000 miles.
My car has an automatic transmission.