When I tried the GSH protocol a few years ago, my baseline FEV1 was 85%. After a year on the protocol, I reached FEV1 of 97%! (this was at age 28 - 29 )
I now take a lower dose of GSH (only 1500mg per day) but am able to reach FEV1 of 103% at age 33. I attribute my scores partially to GSH. I say partially because I do use TOBI if I am culturing PA. I cultured PA for the first time at age 30.
I get my GSH from www.theranaturals.com .
I encourage you to try GSH, especially if you are in the 'mild' category.