Alternator Problem?
 

I have several problems with my 2.7 911

-something is slowly draining my battery down.
-when I first turn the key to the on position before cranking the car the tach needle swings wildly all the way to 6000 to 7000 on the tach. This is before the car is cranked and running
-Once cranked and running the generator light glows but goes out after rpms are above 1000 on the tach like it should
- at night however the generator light stays on even at higher rpms and glows dimly all the time. Do I need a new alternator?

It sounds like the diodes are passing current when they should not. In other words, at least one diode in your alternator has failed. You can remove the alternator and have it tested. As for the tach, check your point gap. The point gap may be too small, should be .012 inch..

I would start with a new voltage regulator and if that works, think of all the money you saved instead of a pricey alternator!

Or you could troubleshoot.