yes you're correct, regular throttle body cleaner contains acetone. Acetone WILL melt/deform the plastic composites of the intake manifold. What you can do is either (what I do) spray TB cleaner on a sponge cleaning swab, then clean the plate.. or.. Use MAF sensor cleaner, it's safe for plastics and it does clean the TB very well.That's what I thought. It's carb cleaner that can allegedly strip the "non stick coating". I've never heard of tb cleaner harming plastics, but maybe???
EDIT: Forgot to mention, if you take the TB off, then TB cleaner is fine. But most of us leave it on the engine while we clean it and that's why you don't spray TB cleaner down the throat of the TB. Most of the more recent cars have plastic/composite air intakes that the TB is mounted on.