Has anyone used the high performance one? What is the absolute max boost a stock s4 turbo can handle? Is it a good product? Thanks.

 

The High Performance Turbo XS MBC (and this is assuming you are talking about the MBC) will do nothing more then a cheap Home Depot ball and spring MBC will do except drain your wallet. As far as the S4 Turbo, I have ran them in the 15 PSI range, but they are WAY out of the effiency range by then. I dont have a Compressor map of the HT-18 handy so I cant tell you what the range is, but I would hazard a guess at about 5-8 PSI...