Glad to see there is another old f**t around here. Don't drive the 5.4 to know exactly but thinking you are right on spot. "Attached a spare hose to it and blew through and it- behaves like a PVC should", know exactly what you are doing, our thinking is the same. Majority are saying, huh? Its a great site and everyone has their mark on it. Good luck and see ya later.
Good old Bill