Vandura

Hello.
I recently purchased a GMC Vandura van . This is my first van and second vehicle with 350 in it.
I ran in to a problem,well actually two and was hoping one of you experts out there might point me in the right direction...
When van starts up and I open throttle rapidly it knocks for a moment or two. Then it smoothes out. This makes me think that ignition advanced too far. In the truck I would check it with strobe through the water pump when looking from the top but in a van I can't look from the top much less stick a strobe light in there . I barely can fit my arm through there. So the first question is how do you set the timing on the van?

Now second question. When engine warms up it idles down a little( as it should) but as soon as it idles down ,in about 5-10 seconds it dies. If you try to re-start it it wuold start and die immidiately.if i let it sit for a few minutes and start it again it would run for another minute or two.
I checked all the rubber vacuum connectors and they are all ok. I thought it could be an idle control valve but if it starts and idles while cold then it shouldn't be it. The van have a bran new wires and distributor cap. Fuel is flowing as it should through injectiors.

Please help me out to troubleshoot it as I am running out of ideas.

Thank you,

D