my car has had recent problems turning off at stops, and it not having enough power to go past 30 mph at times. i got my carb rebuilt and fixed the problem of it not going past 30(im pretty sure it was a choke problem) but that was it. the car still turns off at stops at times. if i sense its going to turn off, i put it in neutral and rev it a little, then go in drive. one thing i noticed is, everytime i put my foot on the brake, whether it be in park or drive, the rpm will go down slightly. as a test, i put my emergency brake on and put the car in drive, and noticed no problems with it. however, when i hit the brake, i noticed the car was about to turn off. im guessing its probably the brake booster, but im not sure. what i want to know is, is the rpm supposed to go down when i hit the brake or not? and if it isn't supposed to go down and it is the brake booster causing this, is there anyway to make an adjustment to it? my brother(who knows more about cars than i do), said i shouyld just replace it but i wanna know if theres some kind of adjustment i can make to it because he nor i am too familiar with brake boosters. thanks