1996 Ford Mustang

I have a 1996 Ford Mustang V6 with 130,000 miles. It has a bad knocking sound. The sound gets less or disappears when on the gas. It is worse when idling and right when I let off the gas. It doesn’t seem to make any noise within the first ten minutes of driving, although it does make a quick knock as it starts. I have read many forums with several answers from Rod bearings to oil pumps.