The ones I have seen won`t even run without the compressor belt on. The fuel and air pressure needs to be within 10psi of each other to run right. The noise does sound like the compressor. The fuel regulator diaphragms can cause problems too. It is a real pain to clean all of the fuel rails but absolutely necessary. The air compressor has an air filter in the top cover that should be serviced too.
The world will not be destroyed by those who do evil, but by those who watch them without doing anything. Remember what He has done and remember that He is not done yet!-- GOD IS GOOD