BRake problems

I'Ve got a 96 with a 4.3L v6, power discs in front and drums in back. WHen I hold down the brake for long times (stop lights, etc) the engine idles rough and may even die. ALso, the braks don't have much stopping power. I think its a vac leak. WHere do I begin? I appreciate any help!

ya, i had a 94 s-10, that had that problem. turned out it was the EGR valve on my 4.3L V-6. Its expensive if you go to the dealer, you can get a manual and try to get it off yourself. What happens is carbon build up blocks the screen on it or something. same thing happened to me. and i was on the freeway. and i have the ZR2, no power steering or brakes.