usually, you can see a darkish deposit when you crack open the blade, instead of the clean aluminum and shiny blade surface when the blade is shut.
there are sprays made to clean these deposits with the throttle body connected, but any that i have cleaned, i remove the throttle body and clean it on the bench. that leaves the intake much easier to thoroughly clean.
i have used different things to clean with, including lacquer thinner, mineral spirits, and spray carb cleaner on a rag.
just make sure you remove any left over chemical residue [if any] so it doesn't affect any down stream item like an O2 sensor. odds of that happening after combustion is almost nil, but you never know........
this may make a difference, it may not. i have cleaned up throttle bodies that i was sure it would make a difference because of all the crud behind the blade, and it did nothing. i have also cleaned some that looked almost new, and saw a dramatic difference, so this was just something that popped into my old, foggy brain, so i thought it can't hurt.
and to others out there, what really causes these deposits to form behind the throttle blade itself, and on the intake ? there can't be THAT much reversion traveling up the intake, can there ?