Well ever since i lowered my car, and ive scraped on quite a few things... some of them pretty bad... my exhaust has gotten quite loud, very drony, and when i floor it, its got a bad splatty sound to it. the exhaust sounds like its all around me instead of at the back of the car. tonight, when sitting next to a wall, i revved it up to about 1500 - 2000 rpm and held it, and my exhaust is making a random, almost thumping sound, almost like you thumped a bass woofer with your finger. soudns like its coming from the muffler section of the exhaust under the car. i took the car to the shop, and they plugged up the exhaust and said they couldnt find an exhaust leak. I dont know how well they checked though... What do you guys think? I dont have the ability to diagnose or fix this myself... could it be possible that i could've blown a muffler out (is that even possible?)? or does it definitely sound like an exhaust leak caused by me scraping my cats and possibly moving my exhaust out of whack? any help would be appreciated that could point me in the right direction towards getting it fixed.