For those of you having surging issues a lesson in how to possibly solve your problem
Sadly I don't have any more complete units and the one left over has the big plastic screw missing. They can easily be resurrected with a little care. First replace the o-rings as they get brittle over time and leak. You will feel how hard they are or cracked when you take them out. Do the fast idle screw first and see if that solves the issue. Then the one under the lid. Those are the easiest to fix. If that doesn't work there are the 2 on the outside body. Last but not least is the one on the large plastic screw itself. Use a wide chisel to unscrew it and get a new ring. Be careful with the threads as it is only plastic.
Then clean all the carbon out but make sure you remember how the pieces inside fall out to get them back the same way. Then comes the fun part and adjusting it. There is a thermo wax thing in the bottom that raises a pin that pushes the cone you took out into the hole in the plastic screw that seals off the air when hot and resumes normal idle. Here is where it gets a bit tricky to do right and not to damage anything.
I did it in a pot of boiling water to raise the pin. Then gently screwed the plastic screw down one turn at a time. You have to seal off a couple of small holes with your fingers and then blow into the outer holes to see if it seats and no air gets through. I hope you are a contortionist?? Alternatively leave it on the car and bring to temp so that the pin rises. Then gently start screwing in the plastic screw until the idle seems normal. If you go to far there will be too much pressure on the pin in the bottom. Adjust the idle screw to proper rpm.
That's as best of an explanation I can give to help you out. There is no magic just a bit of trial and error with the big screw. Perhaps a light coating of lithium grease so the o-rings don't contort when screwing things down. I went to a commercial seal company so that they could take the MM size of each ring but sometimes you are lucky and can find them in a hardware store. Thickness let alone diameter is important. Hope that helps. JS