Jim, at least it's not smoking. Guess that is getting worn out but I still feel for your experience. Anyways years ago when faced with the prospect of kitting mercedes twin zeniths because of all the varnish buildup from gas residue from evaporation in storage. I had one of my insane episodes. I thought gas engines would run on straight laquer thinner quite well. So I just opened the carb feed line under the car and put the feed line in a quart can of laquer thinner. I already knew it dissolves dried gas residue like crazy. Made sure the carb was run out of gas first of course. This is advisable as you do not want your thinner mostly going back to the tank in the return line. Cranked it until bowl etc was filled with the thinner and car started. Shut down and let soak until thinner started to come out the idle screws passages. About 1/2 hour till the first one started by the way. Maybe 15 minutes after till the second one did. Same result as if i had taken the carbs apart, carb cleaned them, and kittted them. No kidding and have used it several times since and will probably again. The only concern I had was if it might attack the floats if they were plastic. That as never turned out to be an issue with carbs that have them. It is probably the limited short exposure to the thinner. Never will understand why others have not done this as far as I know. But if you own cars with two zeniths it is a lot easier. By the way in all of my cases the carbs were much worst than your symptoms as there was no idle even possible on some. Plus the bonus here was in most cases the carbs were in better shape after the cleanout than the last time they were driven. Do not expect this to repair an accelerator pump for example or white metal corrosion problems. But to get rid of the dried gas varnish it seems infallable. Also great for gummed up small carbs. Labour saving, effective and my favorite cheap solution. Pun intended. Since your fuel pump is in the gas tank you might have to run the carb out of gas and feed the laquer thinner down the small tube in the throat to fill the bowl and passages. From your description the idle passages are not totally closed although the thinner would eat through fast enough if they were. But it will work exactly the same. Nothing to loose in my opinion.