Timing problem with 89 G-30 Van

[EricsVan]

Hey guys im having some real problems and so is my local Mechanic on trying to get the timing set on my 89 G-30 work Van. The thing will just barely idle and cuts out sometimes when I start from a stop . At this point im starting to think my Mechanic doesn't know how to set the timing at all. The Van has a 350 engine and 158,000 miles on it. I have had the Throttle assembly and a complete wiring harness replaced already this year. My Mechanic suggested yesterday that I might have to replace the computer in it that this could be the problem. Im running out of money quick . Any help or ideas would be greatly appreciated or any Mechanics in Ga. that you could refer me to that could help me out would be great. Thanks Eric