Acceleration Issue..

I have taken my car last week to a mechanic to try to have him pinpoint this problem and he couldn't find anything wrong. Very rarely when I have my foot pressed down on the brake pedal the engine will rev up as hard as it can staying revved up...if I take my foot off the brake it'll go fine. The first time it did this it overpowered my brakes and almost caused me to rear end the person in front of me. Anyone have any ideas? :banghead:

if it happens again, put it in neutral as qwick as u can, thats really weird.