2006 Toyota Tacoma brakes problems

2006 toyota tacoma double cab has had acceleration when brakes were being applied, and episodes where the brake pedal can be pushed completely to the floor with no brake action what so ever. Have taken vehicle into toyota dealer on 5 occasions with the complaint, but each time have been told that they couldn't find anything wrong (I think their investigation involved driving it around and seeing if the brakes worked--and they did at those times). The problem is episodic, and so is difficult to recreate.

I was creeping--2 or 3 MPH--up to an intersection in my 06 tacoma. When I tried to stop, I could feel the anti lock brakes shifting around, but the truck would not stop. It "drove itself" into the path of a mack dump truck, totaling my truck & sending me to the chiropractor twice so far. If my truck had managed to get another 2 or 3 feet into the intersection, the dump truck would have hit my driver's side door instead of the front tire. Odds are, I would not have survived that crash.