Well, well, well.....Look at it this way.  Almost all bigger bikes are in the 30-40 mpg range so you are doing good anyway.

In truth, you will loose a little because of your mods, but it won't be that noticeable.  The reason is that Suzuki engineered the bike to the really fuel efficient side of things.  Hense you get backfires when stock.  It was LEAN to keep the EPA happy, and to get great mileage.

On mine with all the changes, I get between 40 and 58.  It all depends on how high you run the RPMs in each gear.  If I just run around at a casual pace (shifting at 3500-4000) to and from work I get high 50s.  However, I spent one afternoon chasing a Bandit 1200 through the mountains, and my mileage went all the way to 40...but then I spent most of my time in 3rd and 4th gear and the RPMs were much higher.  It all depends on driving habits.

I average 110 miles before reserve (2.2 gals), so I usually fill at an even 100 anyway.

BTW - people usually complain about the small Savage tank, but in reality those bigger cruisers don't run all that much longer on a tank full than a Savage because their mileage is much worse.  That's why some have those 5 gallon tanks.  They have "range" but low mpg.  Also, I read a review recently on the new BMW R1200 and the MPG was 38  

Enjoy your economy bike

That mileage is what I meant.  Kinda funny when you think that older motorcycles were once really popular because of the good mileage.  Even funnier when you think that my previously owned Malibu with a 3100 cc V6 engine got 29 MPG on the highway....now an 1800 VTX doesn't get much better than that.  Ah yes, the old "bigger is better" issue again  

You'll have a hard time finding a larger tank for the Savage because the frame is shorter than most bikes.  Even a Sportster tank won't give you much more than the headache of trying to figure out how to make it fit.  IMO  8)

You could also be the first known Savage rider with an auxillary fuel tank mounted on the luggage rack, too  

I've seen them on other bikes