It was WAY too early in the morning for me when I read the initial post. I seem to have completely missed most of what you have tried to do to fix it. :-) I am a lot slower in the head than I used to be due to trauma so sometimes I just don't take in stuff correctly.

If drilling holes to let more air in did not increase the idle speed I wonder if it has a bad fuel leak?
A friend of mine had a bad leak that eventually was traced to the promax metering block being out of whack. It was leaking like a blown power valve.