I've been running a weber 45DCOE sidedraft on my stock port 12A for 6 months or so with no problems and now all of a sudden, whenever I rev up to a certain RPM, it won't drop back down to idle. It drops to 2500 or so, if I blip the throttle it will drop again to around 1500, but not to my original 900 rpm purring idle.

I checked the cable, it's not binding, and the throttle plate is clean, I have no idea what's causing this..