Exhaust leak...how to tell where it\'s coming from?**Update** I'm having some problems with an exhaust leak. I first thought it was the EFE valve so I replaced the gasket,and also the collector gasket's (lead doughnuts).. The bolts on the manifolds are tight.I don't know what else to do? The leak sounds the worst when the tranny hits second gear while accelerating. Also is there a gasket between the manifolds and the block?