Earlier quoted context omitted.
Just curious, but how do you know that you are a "holder of the slow gene"?
Probably though 23andMe and the CYP450 enzyme CYP1A2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6212886/
If you ask anyone who works in genetics, though, they'll advise you never to do it. It can be bad news, but there's virtually no good news there.