The VF's were probably the best engine OS ever produced....and you've found a NEW one?? As others have said, forget about the stated HP figures, they're worthless. That weight for the 50SX is without a muffler. Although it's not necessary to use a tuned pipe you'll certainly get a big boost in power if you do. I've only had experience with the 40VF but it's one gutsy little engine, with or without a pipe.