Edited

 

there is no problem with the brake booster, its normal. what your doing is taking the vacume in the booster and letting it go into the atmosphere. if you had vacume gauge you would see that if you pump the brakes your vac would decrease with your rpm raising. and when you stop pumping the rpm would drop and your vac would raise.

your booster works off of vacume. think about it. :^)

 

Edited

 

can anyone else confirm that this is normal? Every other car I've been in, rpms never fluctuate when pumping the brakes.