Two problems

[Phil@sievers.demon.co.uk (Phil Payne)]

OK, gang.  Two knotty ones:
 
(ur-quattro, 1988, 2.2 MB engine)

a) The oil pressure warning light flashes during cruising.  It seems to need 
ca. 30 minutes at 95-100mph - then the oil warning light flashes for about half 
a second, flimmers for another fraction of a second, and then behaves itself.  
It happens, on average, about once every 500 miles.  There doesn't seem to be 
anything wrong with the oil pressure - the sender unit is only a year old.  The 
electrics seem to be OK.  The audible warning doesn't sound.
 
b) At full boost in third gear, the engine sometimes cuts out.  It picks up 
again when the throttle is closed.

Ideas and suggestions for either?

Phil Payne
Sievers Consulting UK
Vice Chair, UK Computer Measurement Group
+44 385 302803 Fido 2:2503/415  CIS 100012,1660