OK,
Here's an update for all those who asked about me putting a 33-tooth pulley on my '05 Silverado.
Pre-33-tooth pulley, I could expect about 41.8 MPG with day-to-day riding, speeds under 75 mph and usually under 65. On my long hauls to GA at intestate speeds 72-82 mph, I got around 34 mpg.
Figured out what I got on my 2,000-mile trip through New England with the 33-tooth pulley, using 12 fill ups for the calculation:
Overall average was 43.248 mpg or almost 1-1/2 mpg higher than my everyday average, but that included a few hundred interstate miles doing 70-82 mph. My low was 39.135 mpg on my last fill up (almost all interstate), which is roughly 5 mpg higher than the 32-tooth days...and my best was 45.261 mpg on a mostly two-lane day (35 to 60 mph), or about 3.5 mpg better than the previous average.
Thanks, Derek, for the pulley.
Conclusion, the 33-tooth did improve my gas mileage with virtually no loss to performance for my tame riding style. In fact, I like the way it feels a lot more. 50-60 mph in 4th gear is just cruising now, and I don't really need 5th gear until I hit about 75 on accel.