Tough question. I wouldn;t say there was anything "bad"........sled had great (better) power and pull and the 4+ lb. weight loss is awesome but, I thought gas mileage suffered a bit. (Granted.......none of these sleds get great mileage) Modifications are definitely a check & balance process.
It's tough to beat this system for the price. Brand new for under $200 you get one hell-u-va performance bang........but you'll lose a bit of mileage for that power.