While I have no specific knowledge of the cams mentioned, I can tell you that *generally* the higher in "levels" or "stages" you go on a camshaft, the higher rpm that cam is tuned for. Also, as you rise in performance on one part, you need to match it with other parts. Generally must past "stage 1" they start to recommend oversized valves, and titatium keepers, etc etc. Those are less rotating mass to allow the engine to turn more RPM's....
If I had to guess, in order to gain more torque on that engine, you need to investigate ways to increase the average cylinder pressure. Either a high compression piston or head work in order to raise the compression as generally aftermarket cams are higher duration which means the valves stay open longer leading to a LOWER charge pressure.
