I'm not sure Ironmike is running pushrod oiling. IIRC I *THINK* he is using Hughes rockers that are shaft oiled.
If it's in the pipes but not on the plugs it's probably exhaust seals. Can you post a picture of a spark plug? I'd like to see your tune up.
Also, you should have someone follow you and not if it smokes on decel or while at a long idle.