My truck wants to die when I put it into drive why?

I have the same truck .. I'd check out the throttle body on this issue, since the TPS has already been considered. Clean it up and see what happens.

Run engine to operational temp and shut it down, clean throttle body, remove and clean the IAC and passages, reinstall the IAC, start engine and wait for it to clear out the cleaner and start idling, shut off engine, unplug the IAC and see if it will start and idle at a very low speed, if it does then plug in the IAC with the engine running, if the idle speed increases then the IAC is operational and that should be it. If the idle speed does not increase then the IAC is not working or you have computer or wiring issues. All of this is assuming that everything else is up to par.

look for any vacuum leaks like at the brake booster . or loose broken vacuum lines .

Your "95 Truck is pre-OBDII, so those diagnostics aren't available to you, and in todays car repair world, it will be a pain to find a mechanic who will be of much help..... As the truck is twenty-seven years old, your problem might be that transmission internal fluid leaks are frequently causing forward & reverse pressures to offset each other and lock up the torque converter. Or it might be a clogged exhaust; maybe a failing catalytic converter. It might be a faulty MAF/MAP sensor, misreading vacuum and causing the ECU/PCU to improperly apportion fuel & timing..... Frankly, people who don't know how to work on cars, a seat-of- the-pants skill we learn over time, shouldn't own old cars: paid help is very expensive.