Might want to consider the stock head pipes if you still have them, gut the cat and use your existing slip on mufflers. Or often you can find someone offering stock headers with a gutted cat. This would be in my opinion the most economical means to regain some torque.

 

107" is no biggie, but you start looking at other things with that many miles and age IMO. It's just a roll of the dice. I personally wouldn't do the build without have the crank looked at. At that point, I say do the whole thing and have the crank R&R by Darkhorse and do a case bore to get 117". But now you're all in for a new exhaust too.

So what would I do? Get a late model Rushmore 103 or a used M8 and get more power, less miles, and a newer bike for probably 5-10K instead of spending 2-4K on a 107 kit that will need new header, tune, etc. Or be happy with what you have.

 

Do the FM 107. I don't think I've ever read one bad post about someone being unhappy with the outcome. Aside from exhaust and tuner might want to consider a clutch upgrade too.

 

What you rally want for that rev range is more torque, rather than power, which is where a proper 2-into-1 comes into its best. My old Glide has an S&S 107" and I have had both TDs and a Supertrapp 2-into-1 dyno set-up. Headline numbers for both were very close, not enough to argue over, however low/mid range torque was as much as 15% better with the 2-into-1, with the added bonus of the engine running much more smoothly. That alone is worth the change from TDs IMHO.

 

I'm partial to FuelMoto. They're doing an engine upgrade for me in two weeks... but there are many good shops represented on this forum, with their own engine upgrade parts preferences...

Whatever shop you plan to use, contact them. If you are going to use their combination of parts for an upgrade, chances are they have installed/tuned many versions of that upgrade. Tell them what your goals are, and then follow their advice.....

If you use the FuelMoto 107 kit, I suspect they will tell you to lose the dual exhausts for best results.....