I wanted to make this last post regarding my problems with the rattling in the lower intake manifold on my 1997 5.4 E 250. My intention is hopefully to help others who may run across this problem. In the beggining I found it very difficult to find any information on the subject and equally difficult to find the part and there was only one left. To start no one believed that such a noise could come from an intake manifiod and I was baffled as well. Again the loud rattling noise was comming from the rear of the lower intake manifold, I did'nt even know there was a "lower manifold'. Mounted on the front of the lower intake manifold is A "manifold tuning valve" that regulates air flow from what I understand is based on RPM. Bolted to the manifold by to small bolts ten and two oclock. the two oclock bolt cannot be removed because it backs out against the engine casting behind the water pump.( if someone knows a better way please let me know for the future). So the intake manifiold has to be removed to access the tunning valve which is a task on a van. In the end I have replaced the tuning valve and re installed the intake manifold. My van runs great and the rattling is no more. Long story to get to a point if you hear a loud rattling noise comming from the rear of the lower intake manifold on a 5.4 Tritton it may very well be the tunning valve on the front of the manifiod, mine was.

A shout out to the guys who offered help your input led me to the answer to the problem. Thanks!