I just recently bought my camaro, and as i was test driving it, previous owners claimed they put a new fuel pump in and has made this low intermittent harmonic noise in the back, i could usually hear it when i am a stop , and it will start up for as long as 30+ seconds then stop and restart again, is it possibly the fuel pump, used car inspection said everything was ok, is it suppose to make that noise? Thanks for any advice yall can give me.