Im fairly new to this, i have a 03 le raptor and is completly stock. Last week i was at the badlands and the muffler fell off. If i leave the muffler off im asuming that it will run lean. I just ordered a pro flow intake so i need to buy jets or a jet kit. I was wondering is it bad to run it with out a muffler and am i going to lose a lot of power? and what jets or jet kits to buy and what jet size i should start off with?

thanks for your help

 

You are looking at possible valve damage if you ride it hard with no backpressure (muffler). Ask other riders around you what they jet settings they have. Different altitudes have varied settings. If you are going to change your intake (airbox) and output (muffler) you will have to do those first. Then adjust your jetting to accomodate the new air flow. Hope this helps, and respect your fellow riders.