The coating is there as folks have said to stop the gunk from sticking. Well after 110K miles mine looked like this
SO you can see the coating really works
I dremmelled the whole lot and removed a lot of stuff so it now looks like
So I definately have have no coating left and guess what, the car runs fine (if anything better) and it hasn't effected the idle at all
So moral is dont worry about the coating, being clean is more important
By the way, my web site has an article on how to clean out the TB so you may want to have a look, details in sig
Have fun
