Q: Truck runns like crap, after driven for a while . on 1990 Ford Ranger

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I just Replaced the fuel pressure regulator, because the truck was running like crap and there was gas in the vaccum area. Now the truck runs great when you first start it up. But if i drive to town and shut off the truck and go in a store, and come back out to go home the truck runs like crap, then just after just a litle while it runs great again, untill i shut it off again. Question 2... The truck also seems to not have much getup and go. Any help would be great
(1) Answer
I would wonder where you got the fuel pressure regulator. It is very important to get just the right one that has exactly the same calibration code as your Explorer, or you will get really weird running problems.