1992 Chevy Astro won't stay running

Engine Performance problem
1992 Chevy Astro 6 cyl All Wheel Drive Automatic

The local mech. Put a new fuel filter and fuel pump on and it's still won't stay running now doesn't know what it is he going to try a couple of other things what should I do when he puts these new things on and it doesn't fix it.

updated 4-4-10
It turned out to be injection module it was $56.47 and he put on a used tire which I did need it was $30.00 that's all should have been done and the finally bill was $375.45