I have a sunfire too with the same year and mileage. I just took it to a shop with the same complaint, (creeking noise when you hit bumps). Who ever told you nothing is wrong, was wrong. The car doesn't make that noise for no reason. I'd take a look at the exhaust hanger. That was my problem, due to the pot holes all around Massachusetts these days, my hanger snapped off, causing that creeking noise, which bugged the crap out of me. needless to say the noise is gone now. So good luck!