If there is a good bit of build-up on your throttle body, you may want to check your recirculation points.

When I took apart my engine I noticed thick build up almost everywhere. From the exhaust recirculator from the header, in the back of the engine (a cover with a "tube" in it), throughout the entire TB, I believe the lack of air and flow was my problem. Althought this problem, black thick stuff, did not come and go, the poor running of the engine did come and go..
GO FIGURE.
Good luck

88 4runner 22re 5spd 30x9.5 bfg AT
daily driver - weekly off roader.
284,400= Jasper - hello 5th gear!
true Thorley Header - V6 3rd
Valid inspection sticker (289,000)