Okay so im new to this forum. but i just read the first 11 pages worth of forums and got all the way back to 8-11-08. and still wondering. So i did my research. But which would be better for me a 13 or 15 front sprocket? and i can keep my stock chain correct? i will be doing riding on trails but more on the track. which leads to another question of how much are the fuel injection kits? nobody talks about them?!?