as of right now, there seems to be about ~10-15 whp gain from these stage one skunk2s. this seems to be the sad truth until there is a true tunning unit for our si's. without tune, these cams wont see their potential due to lack of tuning with respect to cam angle/timing, ignition timing, and air/fuel ratio. on the other hand, these stage ones are an excellent choice if looking for a moderate step up from the stock cams because u can usually pick up a used set for cheaper or same price as type r cams. plus, u dont have to upgrade valvetrain for the skunk2 stage one.