The Parts Manager at our local Autozone advised me not to use any type of throttle body cleaner on my '02 F-150 5.4L V8, since he said it's coated internally with a corrosion inhibitor. Is this true?

 

Yes, it's coated, but there's no problem with cleaning it. However, you need to remove the TB and clean it by hand, don't just spray it down on the engine. Make sure you also clean out the EGR passages in the adapter elbow, pipe cleaners work well for that.