mstein,
I switched to Symdeko this past March, after taking Kalydeco for four years. When I started the Kalydeco, I too brought up loads of "crap". The volume of phlegm was MUCH more than usual, and it was mush thinner. For me, this lasted less than a week. That was more than four years ago. My cough hasn't returned since, except for three periods when I couldn't take the Symdeko or Kalydeco.
As others have said, hopefully your present congestion is just a result of the Symdeko thinning out the crap that has built up in your lungs.
Good luck