My 92 Sonoma 2.5 l automatic starts great, runs smooth, but start driving and come to a stop sign or red lite, engine shudders, most times sralls. Also brake pedal like a rock....no brakes !! Other driving situation o.k. no eng codes. Im not a mechanic by any stretch. I read posts and other stuff on line . Replaced idle air motor. Cleaned e.g.r. Sprayed carb clean everywhere to find possible vacc. Leak. Nothing. All tune up stuff is less than year old. Just about gave up. Then my bud that has old chevelle with big motor made suggestion. I ended up following his advise and got a vaccum resivoir from Jegs for $30 . Problem solved. Just thought id throw this out there, as it drove me crazy for months. Weird stuff seems to happen to me. Had '85 Caprice....started great, idled great, but wouldnt go over 25mph. Local shop finally figured out the return spring on the manual fuel pump was broken, not letting it get a full stroke , so miinimal fuel going to carb. ......weird ****. Thanks.