I've searched every thread about rattle noises on here and can't find one the same as mine. I installed resonated test pipes first and started getting the rattle between 40-45 mph. Found the O2 sensor had vibrated loose. About a week later it started again. Not the sensor. So I assumed the resonater had busted loose since I had megan tps and heard a lot of people had it happen to them. Got rid of the test pipes for HFCs. Still does it. Found a thread thatsome guys had the transmission valvebody replaced and it stopped. Replaced the valvebody when I did the transgo shift kit. Still does it. But the speed at which it does rattle has changed to between35-45 MPH now. I've gone over every nut and bolt on the exhaust and everything is tight. Heat shields are not loose. Its coming from the same area as my hfcs/ transmission/ wheel well. All mods are in my signature. Any help/ ideas would be greatly appreciated. I know that the resonance point changed cause of the HFCs which makes me believe it must he coming from the exhaust but like I said everything is tight so I'm stuck.