[txhokie4life]

Mark,

Preaching to the expert here.....
If you do get it started and let it warm up to temp (oil).
If you shut it off -- is it still slow cranking? (isolate temperature as factor)

Another factor might be to watch the voltage drop in the two cases. V=IR,
so if you can't measure I, you can infer it by looking at the voltage at
the 14pin post while cranking (or any other convenient power point). This might not tell you
why -- but will tell you the starter is working harder or you have that you have a high resistance.

you could also measure the resistance of both power and ground to/from battery to starter
and compare to your "nice" 928.

I'm using 20/50 in my '82 Euro -- new Battery -- but I haven't completed
my ground cleanings and even when cold I fire up pretty good.
Usually 2 revolutions at most and she ignites.
Haven't observed actual voltage when cranking tho.

Mike