the vacuum lines on that carb are critical. especially on the auxiliary accelerator pump. with the truck idling pull the vacuum line off and the truck should run rough for just a second and smooth out. an o2 sensor can cause a running problem with a carb. not usually at idle on those trucks. they are rpm dependent and are electronically controlled vacuum operated mixture solenoid. these systems usually are very sluggish throughout the whole power band when not working correctly. power valve problems usually causes hestation at part throttle. if this carb sat a while with gas in it it may need to be taken back apart and to be sure it is working.
