I purchased one of these 170 kits back in 2006 for my DTR. Only issue I had with it was that when you tightened up the power valve, it didn't rotate as freely in the cylinder as it should do. The YPVS motor was having difficulty moving it, it was that tight. I made a shim which cured this. Other than that, it was fine. I can't say it gave much of a BHP difference over my lightly ported 125 cylinder though.