Personally, I think all the attempts at procuring a taller gear ratio for the stock NA's are going to lead to lot of disappointment.
When those of you getting tired of the short 1st. gear find out that your new ring and pinion only offers about a 5mph increase in first gear (that's about 40mph) your going to notice it's harder to stay ahead of those sporty 4cyl, Japanese hatchbacks at every traffic light.
The others who want their engine to be idling down the highway around 1700 RPMS at 75mph are going to discover that the Crossfires MPG "Sweet Spot" seems to be somewhere between 75 and 80 mph with the stock 3.27:1 differential.
So unless you are a frequent flyer on the Autobahn, chances are you will never realize an improvement in mileage. Because you will have to be traveling so much faster to reach that perfect RPM, the wind resistance you will encounter at that high speed will take more fuel to punch a hole into it.
But on the other hand, it's always good to dream.