A few modifications to this chainsaw produces big gains in cutting speed and torque. Shredder was modified and fast. Shredder II is the same Stihl 039 with 28" Rollamatic ES bar, RSLF chain and tuned rakers. BUT I have "super-tuned" the intake/exhaust, set RPM's @ 13,250 and plug gap at .025in. BIG chain speed and horsepower gain. It runs with less heat and will last longer overall. The improved air/fuel flow combined with an exhaust that allows the engine to "pump" at it's optimum rate maximizes your saws ability to maintain high RPM 's and torque while maintaining cooler engine temperatures. Turn your oiler all the way up and plan on an oiler mod as well. Works for all 1127 series chainsaws. REMEMBER, on any exhaust modified saw, to pull and trim the limiter tab on the high jet screw and turn 1 1/4 turns from seated to richen it and not grenade your new friend. This saw weighs 20.0 lbs. wet, so if your worried about your pea shooters, this baby will pipe them up too!...