Hello to everyone in this forum. I am a new member and could really use some help. Ive recently purchased a 2006 honda civic si and have been having a few problems. The problem that i am looking for help with is i jave what sounds like a fast paist rattling noise heard from mainly under driver floor board or possible from behind the dash but its deffintly on the outside of the car the noise seems to start in 4th gear and becomes loudest in 6th gear and its a constant noise but will go away as soon as i let off the gas and it is not there in idle or if i jack the front wheels up and go threw the gears like normal i dont hear it then only when driving down the road it almost sound like an exaust leak but its not because ibe replaced all that trying to eliminate the problem its also not heat shields becasue ive also removed those hoping it was the problem but nope still there. So please to anyone who has had this problem or might know what it is im lookong for any assitance cause it driving me nuts thanks in advace.