I've used the Prather Mod Kit in the past. What you get from Prather is a waste of $$ to me. You get the brass slide exhaust system, stainless steel skeg (the stock one needs to be removed per them) and a K&B racing needle. Their changes include hollowing out the stock exhaust ports on the lower unit. Talk about LOUD.. Also, the slot for the carb needs to be changed into a venturi. Your best bet would be to put a red / purple / gold carb on the motor and pipe it. Other options are to port the sleave, advance the exhaust timing, etc if speed is what you are after.