I may be biased because I have one but am very very impressed with them. Runs like a stock sled with LOTS of power. The midrange can sound a little gross when there is zero load like when going down the trail, but cleans out instantly when loaded. Has never caused a hesitation when in a tight spot (which was my experience with the M series turbos I had). Fueling compensates for altitude and temperature so I have never touched my boost it box. I think there are a lot of good kits out there now and TSS is definitely one of them.