I had a Ford pick up that ran great cold but crappy when it warmed up. It was the timing. It turned out that the comuter was in control of the timing when it was cold, but when it warmed up it wasn't.
Not quiet sure where the elec choke is on the 2.5. I have a thottle body. You are right timing would always run bad, unless the computer auto adjust the timing. Which I believe the 2.5 is auto timed.