High RPM's

[datzenmike]

Gasket leak....

 

I have never seen an intake leak that made an engine rev up. A vacuum leak adds air making the idle mixture lean which would lower the revs. If you engine revs with a manifold leak then you are running rich or with the choke on.... same thing. Added air will make it rev up.

 

Affects idle almost exclusively. It would lean out the idle mixture but as the leak doesn't change with throttle opening and as intake vacuum is highest at idle the leak is much less of a bother as you rev it up.

 

If it affects mid range, the leak is so big it can't idle.

[racerx]

I would take out the adapters and lay it flat on a table to see how flat it is. These 2 piece can easily be warped, specially if you tighten too much.  If possible, get a one piece, less prone to leaks.  I would spray some brake cleaner around carb area, specially the adapters and if your RPM goes up, then that's the culprit.

[hang_510]

Try snugging the nuts.

Won't that make it squeal like a loose alternator belt?

[Stoffregen Motorsports]

No, that's tugging the nuts. Squealing only occurs when tugging on their nuts.