1991 Chevy Blazer rough only when cold

Engine Performance problem
1991 Chevy Blazer 6 cyl Four Wheel Drive Automatic 250k miles

hi, just bought it. Want it to run good ALL the time. When I start it cold it needs my help to stay running by pumping the gas as its idle slows or quits. Within minutes its improved, it gets a bit better yet still rough. Pulses a rev. Surging. Can't move it yet. Would stall. But can ease off the pumping of gas and let it run. Have to let it run about 10 min prior to moving it if I just want it to go like it should. I'm impatient though. And experienced with tough running cars etc. So I work it through a few start/stalls as I reverse out of my lot and drive to the road and leave. Once i'm over 20 I can stop pumping the gas and it goes hesitantly down the road. If I have to stop. I have to put it in neutral to keep it running until I move again. Then have to pump it to keep it running until its over 20mph again. Heated to 200 the engine is smooth and well running. It runs hot all day long and I can't be happier in it then. The oil runs at 30 or so. The heat at 200 or so. Nice n even. We've done a complete tune up. Replaced the 02 sensor, injectors and the temp thing on the intake. (I'm not the mechanic, thats my neighbor). We're thinking a vacuum leak. But would like someone else's say so. So. My question. What's your say-so? Thanks for your work. Admire the men with the knowledge you know. :) Have a great day! :) (PS: i've spent 1500 on the truck to purchase it and 500 in parts now. I've nothing much left and my card doesn't allow me to use it without more than 100 in the account or i'd have gladly donated :( sorry I haven't got it truly)