Basic Chemical Structure
Both carb and TB cleaner contain between 20 and 30 percent acetone, which is a good all-purpose solvent for any kind of hydrocarbon. Carburetor cleaners tend to use the very aggressive but quickly evaporating toluene to melt resins, whereas TB cleaners tend to use the slower evaporating and less-aggressive xylene to break apart heavy soot particles and oil. TB cleaners generally contain higher quantities of glycol ethers, which slowly evaporate, repel water and act as a "soap" to make the metal surface slick.
Myth Busted
Contrary to common belief, carb cleaner isn't just "throttle body cleaner with some extra oil to lubricate the parts." Carb cleaners specifically are designed to aggressively dissolve a thin layer of resin then evaporate as quickly as possible. TB cleaners, on the other hand, are lingerers; they sit in place for a while, breaking heavy carbon apart and leaving a slick surface to keep carbon and oil from sticking in the future.
Applications
Yes, you can use carburetor cleaner to clean a throttle body, but not without making a few compromises. Carb cleaner doesn't penetrate and hang around to break up heavy deposits, so you'll end up having to use more of it in multiple passes to remove heavy carbon buildup. And when you're done, you've got a TB that's squeaky clean, but will quickly accumulate more carbon and soot buildup. So, while you can use carb cleaner on a throttle body, you're better off spending the same $2.95 on TB cleaner specifically engineered for the task.
