Bigger cams will only move the power to the right on the graph. Yes there may be a tad more of it but you will loose a whole lot down low. Same goes for putting a different plenum on. So its a trade off. May be worth it, may not, depends on exactly what you want to do with the car. Also note that if you upgrade to the wrong cams (generally anything massive) you will need to delete the VCT solenoid on the intake, which will also hurt low down torque and power. I think the HKS 256mm drop in does let you retain vct? (someone would have to confirm that) so that, or one tha tdoes, pretty much the only one you should realistically go with