Could be a variety of things, major or minor. Exhaust leak, lifter, rocker...
Use a screwdriver, pipe or hose. Put it up to your ear and probe around to pinpoint where it's coming from.
You can use a store reciept or thin paper to find an exhaust leak. Move it around close to the manifolds with it running. You will see the paper pulse if it''s leaking.
Thanks I'll try this tom. Honestly sounds like it's coming right from a header towards the firewall or under the valve cover passenger side. I'll have to get it running again before I can determine where exactly. Thanks