Originally Posted by 1SICKM
Difference between 625/650 is crank and blower pulley and tune
We also use a different injector on the 650 than the rest of the lineup. The increase in boost is part of what adds power but the 650 software is very different than the 625 software. VT2-625 is your best all around setup if you want very good power on the stock motor IMO. The VT2-650 is very dependent on fuel quality as it maxes out the stock motor and fuel system. The 650 kit was designed for customers who want to squeeze every last HP out of the stock motor and are ok with pushing limits. It is also meant for customers who understand that you have to use the product as designed due to the added stress it puts on the motor.