i did this today to my moms volvo, i used stp throttle body cleaner that i got at autozone.
i sprayed it in the throttle body itself with the valve closed and cleaned the outside area of the valve, then i sprayed it onto a clean rag and used my finger to push the valve open then i cleaned the area on the other side of the valve (where the seal between the throttle body walls and valve meet), and the other side of the valve itself.
it made a HUGE difference
it was dirty as shit in there, and now the car runs fucking unbeleivably..i have 1000 more rpm's in all gears, it doesnt wind out as quickly, the engine isnt working as hard, and the manual shifting is much much smoother while accelerating, it accelerates much more quickly, and sounds better too.
i wouldnt expect these results though if your car is maintained well, not that my mothers isnt..its jsut that no one ever cleaned the throttle body before
(i also sprayed compressed air through the air filter and cleaned out the airbox..there were leaves in it lol.)