Can someone tell me,do you need to rejet,if you do nyrocks muffler mod?

 

You can probably count on it. It entirely depends on how much you open it up. The more holes in the muffler, the greater effect to the engine therefore requireing jetting adjustments.

 

scully
It may be necessary , the mod lets the exhaust leave without the restrictions the origanal exhaust has. If you have intake mods, that let more air in then you will probably have too.Its all about fuel and air by weight, free flowing exhaust gives the ability to add more air, more air needs more gas to keep the ratio right. the ability to move air through the engine should create more power.