I have this weird noise the the dealershiop can not seem to find due to their.. well never mind heres the deal, fyi this car is a 5-speed
when in first starting out it makes a slight "rattling"
sound all most everytime which i think is because im not iving it enough gas,
then in every other gear when im at about 18-22 hundred RPMs a nasty rattling sound happends, not the typical lack of power sound a severe rattling, the dealership said orrigianly that it was a heat sheild, NOPE! then my windsheild washer fluid resiviour. NOPE then a peice of intermediate pipe in exhaust NOPE!, hmm can anyone please help me im stumped and dont know what to do next.

please help