1998 Silverado dies in reverse and chugs at idle speeds of 45 mph and higher
 

Not sure what's wrong w the truck. I think my mechanics are scratching their heads too. Just changed cap and rotor 3 months ago. Was hard starting and so changed the starter a month ago or less. Now dies in reverse (right after we changed the starter) and chugging on the highway at 45mph or higher. Works better when warm. Relatively new fuel pump(4 yrs). Don't wana throw a bunch of parts at it. Help.