hello frysk.
My daughter was diagnosed nearly two years ago in a very similar situation. Although we didn't have the newborn screen here, she was tested for CF because she was born with a meconium plug (not quite the same as meconium illeus -- usually a symptom of CF). We discovered she had one common CF gene and one very uncommon one (not novel, but only 5 others with it). Like you, we were told that they don't really know if/when she'll develop symptoms. We were told to be hopeful because it was a good chance she would do quite well.
Her first year was tough. She developed several upper respiratory things and eventually wound up hospitalized for a CF exacerbation and on IVs for three weeks. This was 14 months ago and ever since she has been doing fantastically. Not one cough, no need for antibiotics, just doing great. She had a bronchoscopy and it showed she has no mucous in her lungs, no current lung involvement. She's a bit small and struggles to grown, but is considered pancreatic sufficient and takes enzymes anyway.
Our day to day life is the same as every other kid with CF. We do her vest (CPT), we give enzymes and vitamins, and high cal diets. We neb albuterol and pulmozyme.
We've thought long and hard on this and have decided that we'd rather look back 20 (or 30 or 40) years from now knowing we've done everything we can to keep her lungs healthy and hope she'll still be doing as great, rather than look back and know we didn't do everything and wonder if her lung damage was our fault.
I know the unknown is incredibly difficult to accept.
I don't know when symptoms will really show themselves. I hope her lungs will remain