Hey Gary,
Sounds like a normal thing if your running any kind of cam with more than stock overlap. You can add a vacuum canister to "store" vacuum while under acceleration. Check with Cobra Ed, he had a similar problem with his power brakes and I think he went to a canister..... but I'm not sure.
I had a similar condition with another car and just learned to live with it
... either that or I was just too lazy to do anything with with it
- Jim -