Yeah, not cheap and don't work
They work for what they're designed to do. You can't blame the part for that.
I aksed the vendor if any of the rubber seal would work
Rule #1 about parts department drones: Just because a person on the phone or at the counter thinks or even knows something will fit doesn't mean they know squat about mechanical design or operation - or even what you're talking about. (yep, nozzle fits in the fuel tank, engine should run with that liquid -- even if it's water or kerosene) They assume you're an expert and you assume they are an expert. No good can come of that.
Don't start altering original designs to make something do what you think it should do. You'll just be shooting the parts cannon at the problem. Those Japanese designer guys are pretty smart and knew exactly what they were doing when they put it together the way it is. If they say felt goes there, put felt there, not something else.
Are you certain the leak is through the throttle shaft gap specifically? There are a lot of other places and parts that are more likely to cause air leaks or similar symptom problems. It takes a lot more than a less than 1/1000th inch gap air leak past a throttle plate shaft to cause vacuum related problems. Think in terms of vacuum pistons, jets, needles, fuel and air passages, sync problems, etc which cause great levels of pressure or fuel flow differential.
What is the book numbers for the pilot screws. If you just keep turning them randomly hoping it will get better, it won't make the problem go away.