i tried one of those electric vac. pumps last year. did'nt pull enough vac. for me and pulls alot of amps. i tried it with and without it on the chassis dyno and lost a few hp with it on. these pumps came on s10's and corvettes that i know of. jegs sells this very same pump for $250, i'll sell mine for $75, used one season.
mine pulled 3.5" vac.