I'd pour through this. It will take you 3-4 days of googling and reading to figure it out, but will describe how all this stuff works (specifically the CBS up-regulation and CBS plan of action section). Also can order amy yaskho's books.
http://www.heartfixer.com/amri-nutrigenomics.htm#mthfr%20a1298c:%20%205,10-methylenetetrahydrofolate%20reductase%20(%c3%9e%20bh4)But basically if i remember correctly w/ CBS upregulation you probably have sulfur and ammonia issues. Molybdenum and sparga for sulfur detox, and yucca/RNA Support formula for ammonia. I'd also order sulfur testing quanto pee sticks. Usually w CBS if sulfur is high ammonia probably is too.