until you find the air leak you are just spinning your wheels, and it has to be air. If you can't figure it out take it to shop as he said it takes a tremendous amount of air to do what your saying. Put a clipboard in front of tb you will find your problem. I had a detroit run away once and you can put whatever you want in front of that inlet and it would eat it for breakfast, put a piece of plate, clipboard, book, something in front of tb and you will find it. hole in intake boot! Were talking the basics of combustion engines