i put it in 5th, as well as 6th, and stepped on it, both times the boost went to max, but rpms and speed barely moved. took time to get either of them up. so does that rule out the clutch? also, it does have a steeda clutch quadrant with the firewall adjuster

 

yes basically what your testing there is to see if the clutch is slipping, if you floor it and the rpms dont seem to jump up into rpm abnormally (aka clutch slipping) then the clutch is not your issue, if you already have the quadrant and adjustable cable you may just need a good adjustment