I cleaned my K&N filter last week. Had only done 6k miles on it, it looked clean but I thought what the hell and cleaned it anyway.
Now my stumble is back at very light throttle openings In my case, dirtier appears to have been better as it made the engine run slightly richer.
And no, I didn't over-oil the filter.
Dr. MOB says.....hmmmmmmmmmmmmmmmmmm
kinda like a 2 minute mod thing when Steve asked everyone to block the airbox....
so, what this is telling you is that the low speed circuits are not operating correctly, and maybe some of those small holes, the leading most ones in the carb throat, are not really clean. More airflow without more fuel flow tends to have that effect, and when you open the throttle further, you get fuel from other orifices in that group, but you still need them ALL clean and operating.
good posting!!! you just anylized (cause/effect) what we carb guys try to explain daily!!!