what up honda-tech I'm new to this..i just recently bought a 93 civic ex auto from some kid and the car is really loud like I'm running a cut off exhaust but the exhaust is all stock. and i went to a muffler shop to put on a new cat and its still loud but theres no crack headers or any leaks it sounds as if its coming from the motor....and after every drive when i put it in park the car idles up and down like it's breathing? can someone tell me whats going on? please..

 

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Check engine lights? Modifications?

 

no mods and no check engine lights.. but its just loud and idles up and down after a drive..the owner before told me he did a head job thats all i know of.