Thanks all for your ideas. I will check out all the items that were suggested and report back. The exhausted a split manifold was done by the PO the weld is tight and there are no holes in the system. I think I will re-time the engine to the BB and see what gives. Timing to the BB may produce knock so maybe a few degrees before the BB??..We have an adjustable timing light. Mr. Langdon suggest 10 BTDC but our 235 is not happy with that set-up.
Thanks, Steve