Welcome to the addiction ct46: Just a thought here. I own 2 MDS 48 pros. I had a very similar problem with both. What it was is the high end needle, physically affected the low end needle. In short the high end was in to far when I adjusted the low end, so the low end was still way rich. I took them to the local engine guru and he had both of them running in about 10 minutes. Boy do I feel dumb! but this info is now in the memory banks. Try taking the high end almost all the way out, before setting the low end to factory recomendation. Then adjust the high end to factory rec. and take it from there.
Happy holidays
Garry