What make engine shutoff when you remove foot from throttle and step on brake to turn or stop at light, it is intermittent. Air valve assembly has been replaced?

I would be focusing on areas affecting engine performance by hitting the brake -- such as engine vacuum. The power brake booster could be causing vacuum fluctuation affecting engine performance. Don't look for the booster itself to be a concern, but air flow - crankcase ventilation - air to the intake manifold -- things like that should be analyzed and evaluated. www.repairpal.com/repair-shops