I don't know if it's any different for the RWD guys, but rocker arm stoppers are generally considered bad in the FWD SR20DET crowd. You're better off replacing a broken/popped off rocker arm then valves, pistons, rods, and heads that could end up damaged by using a rocker arm stopper.
Also, again, in the FWD crowd, it is not uncommon to see +400hp with just things like injectors, turbo, and EMS upgrades. No need to even open it up.