Check the temp sender II (the one on the left cylinder head) if you keep
having problems.  If it fails shorted, which they've been known to do,
the engine will run lean and be hard (or even impossible) to start when
cold.  If it fails open, the engine will run rich and will die once it's
warmed up.

The other possibility that came to mind was a vaccuum leak, but it
sounds like you've already tested for that.

--

David Brodbeck, N8SRE
'82 VW Diesel Westfalia
'94 Honda Civic Si -- For Sale
'86 Volvo 240DL wagon