Computer checks have shown possible vacum leak and other possible problems but nothing specific is indentified. Have replaced plugs, made no difference. How do you check vacuum pressure, smoke test? Van surges when acceleration is taken to high level. It's like either the vacuum is restored and vehicle returns to normal status but then reverts to sputtering after decceleration.

We had put some gas stabilizer NOS from Auto Zone and it seemed to relieve the condition for a little while but problem returned. I am leaning to either vacuum or fuel problem. Anyone have prior successes with this problem?