On a 2004 Gen 1??? Why? What are you hoping to gain from that? Answer is: not much! The early models weren't nearly as restricted by the electronics/software as the newer ones. And being that it's now 13 years old, not many people are investing it trying to rewrite the old ECUs. There's just no market in it. So if you're not going to try tinkering with it yourself, then pretty much your only bet is going to be Guhl motors. And they're just not going to be able to unlock much out of it power-wise, other than maybe raising the revlimiter.
Here`s my two cents. Get it tuned at a dyno in a shop which does flashing. Don`t use a mail in flash service. Or buy a PCV and get it tuned in a shop. Would be about just as good.
The thing about flashing is that the latest gens (US) bikes are pretty restricted and have more useful tuning parameters. The mail in flash tuning/maps don`t have to be (and won`t be) perfect bike-to-bike to gain a lot. People use this service and will be happy campers anyway. They either don`t understand or care about this. And that is all fine.
But your bike is not restricted in the same way. The tuning must be close to perfect for your bike with your setup to gain your moneys worth of power.
What you can expect to gain power wise with the Woolich flash vs PCV:
Ignition timing - a few ponies.probably. Be prepared to pay for all the dyno time creating the map. Doing this with a non instant tuning method as the flashing will take serious time. (But a generic timing map may work good for you if the shop`s got one.)
STP opening maps - more responsiveness and a bit more power at part throttle only.
Or get the Woolich logbox + wideband o2 kit or PCV with Autotune to tune yourself. It will take some time and effort. But hey, its fun. And the next tune after you change something on your bike is free.