Hi there. So a few weeks ago I picked up a stock 08 yz450f. When It was stock it ran pretty lean and popped on decel so after some searching here I thought I found the fix. Jetting. Welp I figured if I'm going to jet I might as well ditch the ugly shorty muffler and got a full Yoshimura rs-2 exhaust. So I rejet to a 165 main. 48 pilot. And moved the clip to the 4th position. I'm at 1500-2500 elev. and 60-100 degrees. Desert. The bike still has a nasty lean sounding pop on decel but rips when I get it on! Now here's the kicker that's throwing me off. Not only is it lean, when I hit 5th gear Wide open for a second and then try to slow down and shift down it feels like it's dying. As if I'm holding the kill switch until I come to a stop and stall. Then it will kick first kick and run like a champ again?! Is there something in the carb that could be getting stuck open at Full throttle and also causing a nasty backfire? Checked for exhaust leaks with nothing there. Also had my pops check the valves when I got the bike and he said they're in spec. Did some searching but didn't find much.