timing and Backfiring Issuse.

I have a 1990 chevy astro, 4.3, 144,000 miles and now it won’t stay running and backfires. It was running great then all of a sudden, it stuttered and wanted to stall. I accelerated then it backfired like a shotgun went off then stalled. When trying to start it, it keeps backfiring loud and when I do get it started, by squirting starting fluid in the TBI. It idles then, I press the gas and it backfires and stalls and don’t want to start again. I don't know if it can be electrical going to distributor or what.
I put a tune up on it with plugs, dist. cap, rotor a few weeks back and it was running great with no problems at all. Please help me if you can and let me know what and how to check things so I can get it running again. I volunteer coach baseball for kids and also mentor and need vehicle for that. I’m on a S.S. Disability budget and that’s why I’m trying to do it myself. I’m pretty handy in repairing but this one has me baffled.
Thank You!

Basically recheck your prior work,everything. Don't assume anything to be OK. Check the distributor to see if the base hold down clamp got loose throwing the base timing off. A loose or cracked dist cap or rotor can cause the same.