If you already have the head and want some top end hp. The pipe will add 10 to 14 hp to the top end. Either CPI pipr or the slp pipe. The head doesn't really add any top end hp just mid range hp. And makes the throttle response way better.
The 13.1 head is good for 2000-5000 feet on pump. I'm was running the 13.6 which is good from 5000 to 10000 on pump. We unload at about 35 to 3700 feet and I ran pump all last year and never had a det problem, but use good fuel.
e-z how did you get the thing can to work with your slp pipe? everything i tried on an after market pipe didn't work so well. this year i will be running another cpi pipeand there can
why not just run a big bore if you only want to run that low of boost?
and to only person i know with the vipec and the hm turbo setup. well lets just say it is for sale and they are going with a big bore this year. the vipec once they get it figured out should be great for many applications