We talking about the stock t/b or aftermarket ?
If it's that dirty, I suspect you need to clean many other parts of your engine bay as well.
Personally, assuming you also still have the stock intake on the car, is remove the airbox assembly and tb and clean them both real good. That will give you some room to work on cleaning other parts of the engine bay as well.
Here's my how-to on removing the t/b: (part of them aftermarket t/b install)