You probably have a SE
ST, the Screamin' Eagle Street Tuner...which isn't super at all. The SEST is extremely limited on what it can adjust, and if you had an HD dealer put it in, the fuel map in it is barely any better than the stock map. The SEST won't wake it up much, even with a hot cam and more compression. And you'll be spending a lot of money to tear-down and rebuild a working bike, for little improvement.
What you need is to find a good builder and a good tuner (the person, not the equipment) and go with his preferred tune-box. Many of the good tuners like the TTS Mastertune, but there are others as well. Tell us where you live, and you'll get several great recommendations. And it'll cost a lot less to get a tune-box and great dyno tune than the pistons, cams, and re-tune you're looking at.
Many of the stock HD cylinders are out-of-round and/or tapered, so the rings don't make a good seal, and you lose power. If you do decide to do the 10.5 pistons and a cam, it's only a little more $ to have the cylinders bored and honed so they're straight and round--and if you're doing that, you can do the GMR Performance 113" upgrade for the same money, since he'll bore your own cylinders. Check the threads on here for the reviews. It's a lot of of extra performance for minimal cost, and he gives a discount to forum members. See dyno results at
http://gmrperformance.com/services/dyno-results/ and
https://www.facebook.com/GMR-Performance-559176144113934/