Won't make 1 iota differnce to top end. All the PJ is is another circuit to the carb, saves the problem of having to have the air corrector to big to compensate for the natural richening of the fuel curve. So, instead of having the carburation either good on the needle and lean on the main or spot on on the main and rich on the needle with the PJ you get the needle right and then adjust the main/PJ to get it right over 3/4 throttle. Not something really needed on a vmx bike.
