Biggin,I have installed a violet secondary spring,ss buttons from HPD and a different helix in my secondary clutch.You can gain 150 to 200 rpms or lose rpms,depending on the hole settings in the secondary.The clutches should always be tuned to the pipe that you have.There was a post in this forum where the guys did a great job of explaining the clutches and how they work.Rick knows where his pipes make power at,go with what ever he recommends to start with,then you can fine tune from there.I know i didn't help much.Still learnin myself.Later.