Modified my engine - ported heads, XP1 Cam, springs, SS valves, headers, etc. Put on a 3.4 pully and took it to be dyno tuned. Engine would only develop half boost on its meter. Dropped the pully size to 2.9. Same thing. The dyno guy said it was because the ported lower intake manifold opening under the S/C was too large. He said I'd develop full boost if I put the stock manifold back on. We had a deep discussion for 30 minutes but we couldn't agree. I don't think porting the top side of the intake manifold does anything to improve performance and would have no effect on the pressure developed within the manifold. I put a ported manifold on the engine only because it was readily available and not because I thought it would make any difference. Does anyone know if an intake ported on the S/C side would lead to a loss of boost and why?
