If all these steps don't help. Then it sounds to me as if maybe you have one or more worn needles. by pushing down on the tops of the carbs your exerting extra pressure on the slides which in turn pushes the needles further in. may be possible to lower them but that may cause a leaner condition elswhere. After trying what everyone else has suggested which is the logical progression and if that dosn't work, then I would pull the carbs and remove the needles and look at them. they should have a smooth progression to them. But when they wear they get a hip to them (excessive wear in one possition)which can cause abnormal reving when off idle. a rich condition without being noticeably rich.
Good luck and Hopefully happy motoring.

image On the Gas till you see GOD!!!! Then Brake....image

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