Originally Posted by Sp Racer

I'd have thought the problem is the exact opposite,

Bottom end is too rich , which has to have a high idle speed to compensate - once the engine "clears" after a good rev the idle stays high until it loads up again...

You just proved it to yourself when you squeezed the fuel line, the revs rise up "very highly"

Make sure you add some more fuel to the top end needle to compensate.....