Can anyone help me diagnose this?

When I start my 90 bus in the morning it wants to run really rough - no
power, hesitates, etc... Exhaust seems to have moisture in it and it leaves
a slight damp mark on the pavement. If I let it idle for a few minutes it
runs OK (after the OX sensor has kicked in?). Once it's moving it runs
great. If I start it in the afternoon it doesn't seem to exhibit the same
behavior. Odd.

Any ideas out there? I'm ordering in the Bentley this week and will march
through the procedures, but I'm hoping that someone can point me in the
right direction early on!

Thanks,

John Runberg
78 Champagne Edition Westy (for sale)
90 Vanagon Carat