I've just about run out of ideas about this so maybe someone can help point me in the right direction. Here's the short story. My '99 WR has been running great for a long time. I have had Taffy (lean) jetting for several years now and it has a lot of power, plug looks good, and has never overheated. My jetting is 35 pj, 45 pa screw (1/4 turn out), 160 mj, DTN clip 3, 60 sj, 160 maj, 1/2 second ap squirt, and fuel screw 1-1/2 turns out. I went to the DTN needle from the DTM when I put in the GYT-R exhaust insert last year. The bike is YZ timed. I have to adjust the needle clip and/or the mj depending on the time of year (temp. and humidity) but it is usually only +/- one clip/jet size. Last September I took my bike to the mountains in western NC. During one ride, the bike started revving uncontrollably. Nothing I could do would bring it down to idle. I had to ride 30 or so miles to get back to the campground with it like that. I had to brake going uphill because it was running so high. The cause was a cracked carb slide and I found that out as soon as I got to camp. I loaded the bike on the truck and didn't ride it again until I replaced the carb slider and o-ring. Ever since then I've been having a peculiar problem. The bike runs normally until I get to about 20 miles (1/2 hour) or so into a ride. Then it intermittently will not come down to normal idle without a blip or two of the throttle. Most of the time it's normal but it will high idle maybe about 20% of the time once it starts doing it. This completely throws off my cornering and/or regular slowing down since I am used to using engine braking. It forces me to use the brakes, which isn't what I am used to or what I want it to be doing. I have done pretty much everything I can think of to solve this problem. I have rejetted/tested every jetting combo I could think of trying to richen up one part of the circuit. My first thought was the needle. I raised the needle but it just ran like crap. I went to a 38 then a 40 pj but it still ran up and otherwise ran like crap-no guts and burbled and popped. I checked the valve clearance. One intake valve was tight. I fixed that and it still does it. I took spacers out of the carb boot clamps to make sure they fit as tight as possible to rule out an air leak. I replaced the hot start hose in case it had a leak. I have sprayed carb cleaner and/or starting fluid all over the carb with the bike running to see if it had an air leak anywhere else. It didn't. I went up incrementally to a 168 mj, but it lost all the top end along the way and it still runs up. I have adjusted the idle setting during these rev-ups but when it comes back to normal, the idle is too low. I lubricated the throttle cables and adjusted them for smooth operation and made sure they aren't binding at different steering angles. Yesterday, just to see what would happen, I opened the pa screw up to the equivalent of a 75 paj (5/8 turn). It was hard to start and ran like garbage, so I didn't even do a road test. I closed it off to 3/8 turn, which should be a 55 equivalent. It was a lot smoother than with the 45 paj (1/4 turn) and ran strong, but after about 20 miles, it started running up again. The only thing I haven't done is remove the cylinder head to see if anything got goobered up when the piece of the carb slide broke off. As a last resort, I'll probably check that this week. I have at least a thousand miles on the bike since the carb slide cracked so anything that would have been sucked in should have been long gone. And it runs very strong regardless of this problem so I didn't think there was a "mechanical" problem. Anybody have any ideas? It ran so well for so long with this jetting that I'm beginning to think it has nothing to do with jetting. Thanks for any help.