I did some changes to my John Deere STX38 lawn tractor. I did another pully swap and new exhaust, I put dual exhaust on it underneath, and had it come out at a 45 degree angle in front of the rear tires. The new exhaust looks and sounds beter than the old stack I had on it. With the new pully swap, it goes about 25MPH. It used to do 16MPH.