Carbon build up in the throttle body

[CrankyOldMan]

I have the same problem, but I also have a supercharger. My assumption is that mine is from blow-by (compression leaking past the piston rings) pushing partly combusted fuel through the crankcase (the "C" in PCV"). It eventually causes my throttle to lag, but it's not so bad that I have to clean it every month.

If you want to stop the symptom--and you've checked the PCV and EGR valves--you could install an oil catch can. If it is indeed blow-by, and you want to fix the cause, you would need to have the piston rings replaced.