My stock g code 406 runs extreemly rich black build up on exhaust tips huge black cloud if I stomp it. I have a flutter ( best I can discribe it ) at about 1500 rpm and the plugs get richer as you go to the back of the engine. It sound great at idle and from about 1800 rpm up. I swapped secondary carbs front to back with no change. There seems to be no place to check manifold vacume but I checked float level and it was ok.
Any ideas where I should check?
Thanks!
