Shamrock

Hey guys I've been a lurker for quite a while but I question now. I have been driving for the fast last fifteen thousand kilometers with stillen headers, sport cats and an akropovich full system exhaust. I never did the tune because I didn't trust our local tuner and I figured the car would tune itself pretty well instead. So I finally got the nerve to tune the car and right before tuning it I emptied out the sport catalytic converters. The tune was a great success. I got 327 horsepower at the hub. I noticed however that when driving the car there is a slight rattling noise from 3000 to 3500 rpm. This only happens during acceleration and not while in neutral. It's barely audible but to a paranoid freak like me it's pretty loud. Could this be because of the empty sport catalytic converters? Perhaps something happened during the tune? Maybe the extra horsepower and the empty catalytic converters changed the frequency somehow and there is just something rattling and everything's okay? Thanks