What you need to do is to determine where the leak is occuring. After you've filled the cylinder with air listen to where the air ia escaping from. If you hear or feel it coming out of the oil dipstick tube.. bad news, it's the rings. If you hear it getting past the throttle body, then it's an intake valve, and so on for the exhaust. If you see a puff of smoke when you down shift, it could be as simple as valve guide seals. This is a commonly needed repair on an older engine, as the seals shink over time. JOE