So do you not use methylfolate or the niacinamide anymore? Is there a balance one could use between using enough methylfolate for productivity and using niacinamide alongside it to control the stimulation?
If find that the methylation/stimulation effects of methylfolate take about a week to 10 days to kick in, so by the time you realize you have been taking too high a dose, it is too late. You then need to lower your dose, but it will take another week or so before the methylation/stimulation effects from the methylfolate you have already taken will subside.
It's possible that methylation has no direct benefit for improving the illness of ME/CFS, and the benefits that people experience arise just from the stimulation effect. In other words, methylation may just act as a stimulant like say modafinil.