Perhaps it can be that the TB itself does not close enough? I have had that with mine... 70 mm is really to big
... but after some tinkering with the end stop I got it perfect. Actually had the reversed problem of revs being too low often, as low as 400-ish and needing to put throttle on it just to get it started. Btw only a cold start issue, warm my car has usually been on target.