To your P&P question: Corey Henderson in TX, Marc Haibeck in IL, Mike @ EES in LA, LOCOBOB ( bob Melbo see Dynomite Heads thread here), Lagaf ( Lee in IL a member here ) I know I left out some people, oh jez Pete from IL a member here.
Welcome to our corner of the asylum!
Jerry's Gaskets or White Racing Products will have all you need to do this yourself on the plenum pull if it needs to go that far. Both of those guys are members here and Jerry is our VP.
On this issue. It free revs fine, hot or cold or both? I'd pull the plugs for a look see and when was the last time the fuel filter was looked after? Also, the PCV valves are okay, not stuck shut? Your air duct from the filter housing to the air horn could be getting sucked shut if the choking happens say above 4-5 k rpms.
On this air duct thing, I've never had it happen to me so I'm not up on the symptoms. I ran across the issue in the "common Issues" section over at the NetReg site under the maintenance tab. I made my own duct liner from some dryer duct when I first got my car. I'm thinking that you might have to rev her up almost to 6 or 7 grand in neutral to see it happen, as I would think it more likely to happen under load? I think you ca get replica ducts from corvette central or check with Jerry's Gaskets.
Tom