whenever i rev teh engine, especially when its cold, the engine makes a metal-on-metal squeeking noise. ive checked under the hood a few times to see if i can listen to where its coming from but i cant figure it out. im wondering if it could be the exhaust, because i tried changing the shifter, and i disconnected the exhaust to do it, could i have tightened the cat bolts wrong? the thing is that it squeeks only when the engine decelerates.... like if i start it up and rev it up, it squeeks when the engine goes down (if that makes sense).. can anyone help me?

sorry for the long *** paragraph

 

i had a broken exhaust hanger that rattle d like that