I installed a PCV on my 2010 FLHTK. I had a stage 1, but I also removed the header (cats), and replaced them with V&H Power Duals and HI-Output slip on's. My intention was to cool the bike down. It worked well. I thought I got a little better torque from this set up, but most people will say this is not enough to give you more passing power.
I purchased mine through FuelMoto USA and it came preloaded with a map for my specific set up, so no Dyno was needed.
I've since installed SE255 cams and I did get it tuned and wow, the bike runs great! Lots of torque.
Is it worth the cost? That depends on what your intent is. Do you want more passing power? This may not do it for you, you may find some increase, but if you really want more power you should change out the cams. Do you want to cool down the bike? This will help, but in my humble opinion you need to get rid of the cats to find any significant change in how hot the bike runs. Better MPG's? Nope, in fact you may lose a mile or two.
You will get a lot of opinions on this subject. Some will offer up other products, I can not honestly comment on other products as I have never installed or even riden bikes with these products. I can tell you that I am happy with my particular set up. I was satisfied with just the PCV and stage 1 with changing out the pipes, but I really picked it up a notch when I changed out the cams!
Hope this helps...good luck!