| Fireman
The first thing to do in modifications is to determine what your ultimate goal is, this can be tough but if you start right it stays right and it can be less expensive.
Budget asside you have quite a few options
Stage 1 = Best HP for $ = SE Air Filter Kit, New Slip on mufflers and tune up carb or flash/dfo/powercommander on EFI bike
Stage 2 = Stage 1 plus cams, a different flash or a powercommander, DFO may work to some extent but it has limited capabilities in fuel deliver only.
Big Bore = Increasing the cylinder size from 88 to 95 inch and adding pistons, usually flat top 9.5 to 1 or cast 10 to 1 with stock heads
You can combine the Big bore option with Stage 1 or 2, however in that you have the motor apart to do a Big Bore you might as well drop in cams, adjustable pushrods, and consider having the heads worked on for a mild street port as they are off the bike anyway, labor savings is the key.
You could do it in stages Stage 1 see how it does if you like it and RTS.
If it's not enough then decide to go to the next level, a big bore is probably a good idea, have your cylinders bored to accept 95 inch pistons, saves $150-$200 over buying HD ready made 95 inch cylinders.
A key to picking a cam is deciding how you want the power delivered, more overall power for two up cruising or stop light racer, or a bench racing high hp monster.
Most opt for a good middle range. some of us nuts, me included just can't find enough power, probably should have bought a boss hoss 502 to begin with LOL
Two ways to do this, choose parts talking with people, on the boards, or a good builder, or buy a pre arranged kit from S&S, Zippers etc.
So let us know what you're looking for and I assure you'll get an a**load of advice LOL
In the meantime do a stage 1, Filter, pipes and tune the carb or efi
Good slip ons come from Cycle Shack and Khrome Werks HP+ they sound good and are not expensive as well as flow better than HD SE> | 
