If your motor stalls when brakes are applied, you need to turn the idle up. Screw it in about 1/4 turn. That setting isn't as fine as the other needles, which have to be adjusted in 1/8 turns. The reason it stalls is because when you push forward on the trigger the carb closes more than if you just let off the throttle. That opening is not large enough at that time to keep enough air/fuel flowing into the engine.
Also, if I'm not mistaken, due to your altitude/thin air, your truck runs leaner than those around sea level. Start with the factory settings and gradually richen by 1/8 turns out. Start with the LSN. Once you can erupt without hesitation/chugging from an 8 second idle, move on to the HSN. Remember, just keep adjusting until it just starts to lose performance, then turn 1/8 in the opposite direction. You will get it, just have patience. I got my truck totally exploding off an 8 second idle. That's the key. Make sure you idle for 8 seconds then just squeeze the trigger, WOT...