I strongly recommend an "alternator delete." This goes doubly for those with already aeromodded cars.
Before an alternator delete I was topping out at 57mpg.
Afterwards I'm hitting 68mpg.
That's just over a 20% gain.
I think my results are so much higher than Darin's for two reasons:
1.) Honda D-series motors are very efficient at low loads.
2.) Low aero drag (and an HAI) make the alternator a bigger portion of the load than normal, therefore removing it gives a proportionately large gain.