'91 200: Minor surging when warm

["EREC - Duncan, Cameron" <CDUNCAN@nciinc.com>]

1.	My engine exhibits a slight surging that increases a bit when the
engine has warmed up in afternoon rush-hour heat.  Distributor & rotor look
okay, have about 15-20k miles on them.  Replaced a couple of vacuum hoses
which improved starting and performance, but still have the slight rolling
surge. I have some Techron I've been meaning to put in the tank at fill-up.
Used some last Spring, but didn't see much change in engine smoothness.  Any
ideas on what I should do to find the problem?
2.	The temperature gauge also does not appear to engage but
intermittently.  I understand I should perhaps replace a brass-encased
"switch" that corrodes due to its odd mount (part name? Number?).  Could
this be partly responsible for the surging?  Anything I should change while
replacing or cleaning existing gizmo?

Temporarily Bentleyless, 

Cameron Duncan, EREC Architect	-	(800) 363-3732	-
CDUNCAN@nciinc.com
Audi 200t sedan - daily driver