ok so i built a superbolt pump and had an nxt shocker reg on it. shot good except i couldn't get it over 260fps( do to the reg only going so high as far as psi is concerned) it had a fart when i held the pump forward and didn't fart when i just let it shoot without holding the pump forward. So anyway i changed springs in the reg to a stiffer string to achieve higher psi. ok so at first it didn't fart then after adjusting the ivg it does know fart.
Question: What causes the farting? is it the pressure or the ivg setting? or is it the valve spring and velocity spring set up?