Joe;

Sure...I read "drone", and probably because you wrote of generators and alternators near the end of your post, thought (electrical) whine...and so I gave you the automotive electrical noise dissertation...oh well...it's still all good info which might help someone out there.

Resistors?

As far as the exhaust drone at highway speeds, about the only thing I can recommend, is to put your car on a comprehensive noise abatement plan, including:
1. Installing sound deadening self-adhesive pads (from audio supplyers) on all expanses of sheetmetal which don't have them (including in doors, trunk, behind interior panels).
2. Installing an under-hood "quiet kit" (I'm working up one for the 122s).
3. Installing a carpet kit...and don't be cheap with the padding underneath, especially that against firewall (fix rain leaks first!).
4. Eliminate direct air passages to engine compartment by sealing all holes (for wiring, plumbing, linkages etc.) through the firewall with foam.
5. Installing a little less "sporty" muffler but still with a large diameter pipe.
6. Wrap header (if present) with fibre-glass wrap.
7. Stuff cavernous hollows in vehicle with open cell foam (allows drying, so doesn't trap moisture) including under rear seat, C pillars from trunk, under dash etc.

If that doesn't give the amount of improvement your looking for, try a set of David-Clarks, wired into the on-board stereo...that should do it!...see below:

and http://www.intelab.com/swem/j5rhistory.htm.

Good Luck