1983 f150 stalling question

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Original owner of a 1983 F150, 302 engine, 2 barrel carb, 216,000 great miles. Now stalling when you step on the gas pedal. Replaced the fuel filter (twice), fuel pump, new distributor cap, new rotor. Checked the vacuum lines and they seem fine. Starts and runs great in park, can rev up and it purrs. Put the transmission in gear and it stalls. Starts right up - put in gear stalls.
If you start and put in gear and let it idle it will crawl along - hit the gas and it stalls.
I am good at replacing parts, not that great at diagnosing problems.
Any help would be appreciated. Thanks

 

[blacksnapon]

generally, you'd be looking at an accellerator pump

 

[[email protected]]

Thanks - is that the pump on the front of the carburetor? I have replaced those before, sometimes the membrane is torn on the inside.
Thanks for the reply!