Enzo: You need to try what I am working on. Try living in the NOW and not worry about all these things that may or may not happen in life. Your lung function is super excellent and I am so happy for you. You need to concentrate on TODAY and do what you can to help your health and whatever else you feel is important to accomplish in your life in this day. Try not to worry about tomorrow as none of us are guaranteed tomorrow anyway and we see that in our lives all around us every day. I am working on all this too and it is just logical as worrying does not change anything anyway but I know how it is and it is hard. Actually it really is good to cough up stuff during treatments or exercising. That means you are clearing it out of your lungs. Try to take it all a step at a time.
Enzo - your PFTs are awesome! Congratulations! With CF, it seems there really is no "normal". I was diagnosed at age 30, and spent most of my life not coughing up much stuff. Though, the last several years have been different, as I now cough out a lot more (thankfully, my FEV1 has been stable). Just keep doing what you're doing, and don't let up!
I don't cough up a lot unless I'm really sick. Maybe an 1/8 of a cup of mucous a day? Perhaps a little more if I exercise but never a ton. Like Hail said, everyone is different. your PFTs are great and it seems that you exercise quite a bit which is very good for your lungs.
Coughing up stuff while working out is great! It's what your body wants to be doing. I think of it as my body cleansing itself of toxic mucous. I do it while running up a steep, steep hill coughing up stuff the whole time. When I get to the top of the hill, I do pushups to congratulate myself. Then I run all the way home. If I've done my workout right, I've coughed all the crap up then and I'm all cleared out for the night and much of the next day My PFT's are also in the low 100's.
As PFT's and FEV1 fall along with more scar tissue build up, one is more and more likely to experience the constant and persistent phlegm cough that many CF patients have. My suggestion to you is enjoy it while you got it, stay as active as you can, and what ever you do, don't slack on the therapy! the price you will pay in the long run isn't worth it.