Dave three things;

1. Go back through the carb and check the idle circuit as said it sounds like the culprit.

2. The worn cam chain MUST be replaced , the guy at the tuners is correct about having trouble timing it. A series engines will run on seriously worn parts. God knows what the cam timing really is . The distributor runs off the cam so your ignition timing is probably variable as well.

3. buy the extracters/headers before the side drafts.....big intake (webers) tiny exhaust (no headers) is not optimal. Intake and exhaust should always be a set of parts.

Keep us updated , Tom