91 P/u

When at stoplights, sometimes my truck idles funny. Like a surge. Only when I step on the brake though. Has anybody had this problem. If so please contact me on some information, because I want to fix it.

Make sure you have no leaking vacuum connections or cracked hoses. The brake booster may have a vacuum leak.

i'm guessing that it idles high when you don't have the brake on. The computer will cut the idle if it is too high and you have the brake on, so you get that surge. Try snapping the throttle and see if the idle comes down to normal. I had a throttle cable that would stick a little bit one time and it would idle a little high. Could also be a vac leak as mentioned.