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Zoom this has a great idea. I would have guessed it to be linkage related, SPFs do have to be adjusted to not force the carb closed at idle and there's always the loose motor mount culprit. Since I've been datalogging stuff and have an air temp sensor in the air cleaner here's what I noticed: The air temp while driving is usually 85 degrees, after stopping for a few minutes and restarting it will be up to 140 degrees while moving slowly in a parking lot, that's enough to cause the air to be considerably less dense. Jcoop, when you tune an engine with the hood up at rest you're dealing with cool air. If you're setting it by rpm you may want to try setting it to the maximum vacuum instead. You could get fancy and keep a vacuum gage hooked up, watch it with the hood closed under driving conditions and sneak out occasionally to make an adjustment to the idle screws. BTW, if you have off idle hesitation it's likely that the transfer slot is overexposed at idle which may also contribute to sensitive idle behaviour. You have to get the slots such that the throttle plate exposes a minimum at idle, it should look like a square with no more length exposed than its width.
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