My 2003 XR650L, featuring XR's Only header and muffler, "Dave's mods" on the carb, Clarke tank (thanks to LakeCleEllum, Bob), opened air box with Uni filter, de-smogged, and running MT43 trials tires on both ends with dual rim locks.
Unfortunately, though, since my bike wreck a couple of years ago this has been the bike I've been able to enjoy the least. I ride it mostly on the street now, with the occasional well groomed logging road thrown in for good measure. Any serious off-road jostling still takes its toll on my wrists. They continue to improve, though, so I'm hanging onto this bike looking forward to the day when I'll really be able to ride it again.