I've seen it on my '99 SVT 'Tour and if I recollect clearly, both my '89 and '93 SHOs had the same stickers on the TB's (anyone that's got a SHO and can check their TB, correct me if I'm wrong).
I've had a very similar discussion before with a mechanic about 8 years ago (i was wary about cleaning them myself, which is why I swear I had those damn stickers on my SHO's). I was told to go ahead and clean the gunk out with a carb/TB cleaner that was safe for FI engines, as my TB's on both the '89 and '93 would get rather nasty.
Now, having said this, don't let the TB SOAK in the cleaner. Spray it and then quickly wipe it off with paper towels or some cotton shop cloths. As you wouldn't take steel wool and gasoline to a teflon pan to clean it, go easy on the inside of the TB.
