yeh I recommend changing the manifold also so you can eliminate the secondaries. I am currently running a skunk2 and had no problems with good mid-range power, but with the stock p72 ecu you will not get the full potential of the manifold due to the ecu still searching for the secondaries. But if you want to do something else besides bolt ons, try getting cams for more power, doesn't have to be expensive or high sought for cams, you can just go with ITRs or CTRs and still gain some good power.