windstar2304

I have a 1998 Windstar with a fuel problem that hasn't been able to be diagnosed. When the car is cold, it runs fine. Once it has run for awhile (about an hour), it has a severe loss of power, with no acceleration whatsoever. Another observation - even when cold, the engine starts to break up around 4000 rpm. When hot, it breaks up around 1500 and has no power. We were on vacation when it first happened and a dealer supposedly diagnosed it (but I didn't get the codes). They said it was either a clogged fuel filter, an inoperative or clogged EGR, or bad fuel injectors. I replaced the fuel filter, removed the EGR - all clear there, and removed the injectors and cleaned them. They all seem to be operating and are in-spec for ohms. I checked fuel pressure and it is just below spec for all readings. Replacing the fuel pressure regulator did no good. The car idles fine, even when it has no power. It seems to be an electrical sensor that gets too hot and fails. Problem is that when the car cools off, it seems to work fine again. I doubt it is the fuel pump itself since it is far from any heat generating parts. Not having an OBDII tester, I haven't been able to diagnose it. And when the dealer finally gets around to checking it out, the car has cooled off too much and they don't seem to want to take the time to get it hot again.

Any ideas where to continue looking?