Porsche doesn't generally throw something in a design without a good reason (or two). The air guide on the back of the alternator helps force more air to the #1 and #2 cylinders since the fan's CW rotation tends to throw most of the air towards the 4/5/6 side. The oil cooler has its own super-nice duct in the shroud to force feed it. Its pretty much that simple, but...
Between alternator swaps, different alternator types (built in VR versus separate), and a general lack of good access in there, all sorts of wierd things happen over time for the sake of getting the job done quicker. Get the correct air guide, hook up a direct ground to the case, and make sure your fan belt runs straight down to the drive pulley on the crank. Any angle to the belt when looked at from the side of the engine means you have the wrong altenator or the install didn't quite go right.
As you might guess, I have inherited more than one messy install in this area from previous owners
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Hope that helps,
__________________
-Doug
1968 911R Clone; 11/07-?? (forever the project car
)
1978 911SC Midnight Blue Metallic Coupe; 7/05-11/09 (so long impact bumpers)
1973.5 911T Sepia Brown Coupe; 9/98-8/99 (went to a great home)
1973.5 911T Gulf Orange Targa; 5/97-11/02 (went back to Germany)