Head
I have run all different heads on pros I have run rk tech I have run brads head and even the pre updated 08-09 dragon head and on these pros 11-12-13 they are too lean in my testing they all will det in the mid range, if you are gonna run compression you need to add fuel, I have found in my opinion and testing polaris (to meet EPA regulations) has leaned out the mapping to help comply and in order to do this they had to drop the compression because of det, I have done this since they updated the dragons, when you up the compression you have det problems not all the time but several times a day it will put you in limp mode, so to sum up what I'm saying here its lean fuel mapping causing the biggest problems for guys when adding compression it's not the head it's the EPA if you want more power you need a controller. There is some problems with fuel quality but in most cases I have seen its the mapping you can make a stock sled run better just by adding fuel just my .02, also I run the rkt head and love it but anytime you add compression anybody's head you need to add fuel on these pros, there are bone stock 13 that are hitting det all the time where we ride with 91 premium fuel, elevation seems to make a difference the low elevation guys don't seem to have as much trouble as us high elevation guys I ride 8-11000 ft