If the bike is stock you may want to consider an alternative....air mods, pipes etc. I know you said you have mods but i'm not sure if you mean accessories or actual performance mods. If the former you might consider modding the airbox, free flow filter, less restrictive pipes, etc. Even irridium plugs made a sizable difference in response when i had my speedmaster. the Bonnie's airbox is different, but the same mods apply. I cut the bottom out which doubles the intake area. Put a uni filter in it, thunderbike pipes, irridiums, nology coils, and jetted it accordingly. I got a pretty healthy power gain from that. I'd bet about as much as the BB will net you. The coils i'm not sure about, but they may have helped the freeway speed roll-ons.
Of course you could always get a thunderbird 1700 with short tors.

One thing about power most people don't realize, or at least it doesn't seem like they do from the things they say, is that having a ton of power is a lot more enjoyable even when you don't ride fast. It's just a whole different feel when the huge power is there even when you aren't using it. Riding is so much more fun for me when i have the kind of power that doesn't leave me wanting more even tho i'm riding sedately. Many people question my desire for big power saying things like "yuou can't possibly use it all" or "you can kill yourself with a lot less power". They just don't get it.
anyways, good luck. And tho it may be the last thing you'd want to do, consider the Tbird. It's literally the most incredible handling bike you'll ever ride short of a sport bike. Several bonnie owners and even a thruxton owner have said they bougth a Tbird and think it handles better. Whether or not thats true, it gives insight into just how easy this thing handles. And with the 1700 you will be way past the point of wanting more power ! Amazing bike. Oops...sorry, i can't stop raving about it even after 2 years !

But thats one possible solution for ya.
