Why does truck stall if I put it in gear

There are many things that can cause this problem... First, is there a check engine lite on, if so, what is the code? Second, recheck your spark plug wires, making sure they're going to the right plugs AND as a bonus there's a tech serv bulletin online about wire routing n misfires. Third, did you at any time loosen the dist. as an ass'y or is it loose now? Fourth, look down the throttle body with the throttle plates full open n see if the floor of the intake looks like a swimming pool of dirty oil, and... Fifth, pull n clean the idle air control on the back of the throttle body, they have a bad habit of causing all sorts of running n idling problems if they're dirty or bad. No guarantee any of these are the problem, but it'll get you started. Question, do you have any warranty with your purchase? BTW, your fuel pressure seems fine. Last but certainly not least, invest in a scanner that'll read live data. You can pick one up starting around 30-40 bucks. N be careful about firing the parts cannon at your vehicle, you'll find, as many do, that'll do nothing but drain your wallet really fast. With these marvels of technology, you gotta be a tech first.

Thank you I'll double check all this your right I've been draining my wallet. The check engine light wasn't originally on but i unplugged and plugged back in alot of sensore so now it is so I'll check that and see what I get