With the tool, you adjust them with the sled off. All it is really is a jumper. You put 12v to the adjuster and plug it into the servo motor and it powers the valves wide open. i will have to go back and read the directions that came with it but I believe you have to do this with the pipes and headers off so you can see the actual powervalves move in and out. I got this from bender racing when I was building my viper.(advatar photo) I don't even know if they still offer them, this was at least 3 year ago when I bought it. Like I said don't hold me to them directions its been a while since I tuned a set.