The C-KIT is no longer for sale i know this for a fact!
Their has been problems with customers installing this kit incorrectly as it runs very high boost and requires deep engine modifications.
The C-KIT impeller produces much higher exit temps and this alone is a negative and a loss of HP.
The next biggest thing is the Turbo and it also requires engine modifications.
All racers run the B-KIT as it has proven the test of time. The NEW B-KIT impeller increases boost with engine revs.