95 G20 Stalls in gear runs rough

I just bought this 95 g20 work van. In park the engine runs fine. When you put it in gear she tries to stall and runs rough. When you apply more gas it bogs down before taking off. I changed the cap rotor plugs egr valve. I have had this at the mechanic for over a month. He has replaced the computer(found penny in it) the prom, check and cleaned the throttle body. Change fuel filter. I am ready to scrap this thing. Any ideas.

I just bought this 95 g20 work van. In park the engine runs fine. When you put it in gear she tries to stall and runs rough. When you apply more gas it bogs down before taking off. I changed the cap rotor plugs egr valve. I have had this at the mechanic for over a month. He has replaced the computer(found penny in it) the prom, check and cleaned the throttle body. Change fuel filter. I am ready to scrap this thing. Any ideas.
What engine?

Any codes or check engine lights?

Any cylinder missing?

What is fuel pressure reading?

Good hot spark to all plugs?

Any restriction on exhaust?

What is engine vacumn at idle and at 2K rpm?

What is timing/spark retard set at?

Also consider finding another mechanic or good repair shop.