I have just put on a full comp Yoshi pipe and a GYT-R filter, pre filter & adapter on a 05 raptor.

For best all around performance (I trail ride and XC race some times) my question is this:

1. Airbox modified, with two 1 1/2 holes per Yoshi, or no lid.
2. Jetting size, is 160/165 Mukuni correct. My elevation is 600 ft.
3. Air fuel screw should be set around what?

Thanks for your help...

 

For the most power you can take the lid off. But if you are going to be racing xc you can easily get into a lot of dirt, dust, water, and mud. I would just remove the snorkel and leave the lid intact.

The jetting sounds a tad rich for your lid on, should be pretty good if you take the lid all the way off. Air/fuel screw you should just start at 2 or so and adjust it until it works the best.