I've developed a noise that sounds almost like a knock in my engine. I've got around 168k miles, and its changes with RPMs, but you don't hear it when you rev, you hear it when you let off the revs. It also seems to be louder and more of a thud when you listen with a stethoscope to the valve covers. I can hear it against the supercharger too, but it didn't sound that loud on the timing cover. Any ideas? I just changed the balancer to that $100 one that AutoPartsNew4U.com sells. Its been sitting 3 months before this, and the noise only appeared after about a days worth of driving. Oil pressure appears to be good (I did the swap to the mustang sensor, so it doesn't give me a number, but at least it sweeps and isn't a dummy light) or at least registers in the normal range for my SC. Oil isn't milky or anything and I didn't see any metal in it. I can take a video if that might be helpful.