Genuine Stage 2 Performance Kit

I purchased the stage 2 kit intending to install it myself but after reading the shop manual I decided to take it to a pro instead. First thing he tells me is that the cylinder kit is a Chinese P.O.S. that the exhaust isn't good for our altitude (I live at 8000ft) and that he's blown several motors with this kit. (I'm dead serious, not what I wanted to hear) But I went ahead and had him install it. ($400 for installation included a new variator as well) Performance upgrade is HUGE, it's like a new scooter all together.Off the line it's got alot more power & going up hill is vastly improved, going home I encounter a monster hill and would bog down to around 20 now it reads a little above 30. The downside, it bogs down between 30 & 40mph, the mechanic said this is because of the exhaust not creating enough pressure at our altitude  & replacing the factory exhaust would solve this. So while I'm happy with the performance I'd recommend talking to your mechanic before buying anything.