After it rains and I start up my windstar it runs at about 500 rpms, keeping it in park I will rev it up and at 1500 rpms I hear a click and then it dies. I have already replaced the egr valve, plugs and wires.

Any advise, please help.

You could be getting some wetness on the relay-fuse box (near battery) causing some issues. Your PCM power and Fuel Pump relays may be getting a little aged ... and therefore need to be replaced. I also suggest pulling all these relays and fuses and lubricating the bases.