Looking at the dyno sheet, it looks like you have a bunch of reversion down low, killing the bottom end. Then the lobe separation and ICL is not letting the torque carry in the higher rpms, which is killing the horsepower.
Read this ^^^^^ and read it well. Your intake manifold is directly connected to the exhaust system. IMO retarding the cam isn't going to fix the bottom end AND add power up top. Smaller , longer collectors will make a big difference in this case. Your cam does not play nice with the induction tract and exhaust tract. I bet if you ran this engine for a longer period of time you would see exhaust half way up the intake port, maybe further. J.Rob
