91 chevy 1/2 ton. Idles and revs fine when in park, but it has trouble running when in gear. what's up?

runs great when not in gear, when in gear it dies at stops and bogs out a little when you get into the throttle. Has new injectors, tps, map sensor, fuel filter, rotor, cap, timing is right at 8 degrees. all vacuum lines good. This is a tbi injected 305. What wrong with this thing? Please help!!!
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