I still have the factory main jet installed. I think I should change it as I fear it could be a little lean due to the new exhaust. The kit is called a stage one performance kit from provoscooter.com. The kit came with technigas RS II expansion pipe chrome, malossi variator, malossi racing cluth spring set, ruima variator roller tuning kit, uni filtered air vent, and I ordered a set of 10 gram roller weights. I put the racing springs in today and the 10 gram weights. It now will go as high as 47mph on slight downgrade. I'm going to need some time for testing different weights and a larger main jet. The biggest improvement from everything is the exhaust. It's a little loud for my taste,but is acceptable.