I've been following this thread and my question would be. Why are you fooling around with this problem. You had all this work done to a tune of a bunch of bucks so why not take it back to the service faclity where the work was done? They should be able to diagnose the problem without much effort. They would probably Sniff the over flow tank to check for hydrocarbons and pressure check the cooling system after the engine has cooled. That would be my recommendation.
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