Just purchased a DRZ400S 2006, 800 miles. Its has an FMF pipe and stock stock header I believe. Purchased the bike in Seattle used. I live in the Cascades at about 2k feet altitude. Riding area will be between 2k-4k but sometimes up to 7k. Currently it does backfire some. What would be the best jetting (Mikuni) for my riding and setup? I plan on doing the airbox mod.