Hello all I just recently bought me a mustang for my birthday. A 1999 mustang automatic v6 3.8. When I bought the car the guy said the harmonic balancer needed to be replaced that's why it was shaking. So I had spent at least an hour calling auto part stores to find one nobody had one, so I went to a junk yard and bought one. On the way to the mechanic to have him put the harmonic balancer in the exhaust from my passenger side just dropped from the exhaust manifold all the way to the muffler tip. So I told my mechanic that I needed the harmonic balancer put in and to fix the exhaust so he did but the new harmonic balancer did help a little bit, so my question is what else could cause this and what else should I check for? The check engine light isn't on and I did a scan for codes and none come up