what brand / dosage of B1 do you take?
I ramped up Allithiamin for about 4 weeks to 200+mg/day before switching to the Benfotiamine by Doctor's Best at 150n mg/tablet. I played around with slightly higher doses of up to 275mg or so a day, then went back down to 200mg/day for a couple more weeks before lowering it to only about 50mg/day--actually 3x18mg which calls for a lot of splitting capsules!) So far this seems to be enough extra B1 for me to tolerate about 20mg/day of Folate and several sprays of the Adenosyl/MethylB12 Oils. However, I also get about 10 mg of Thiamine HCl in my daily 1/2 B-Complex, B-Minus by Seeking Health, which I take 1/2 of/day in two divided doses. So that's a total of a bit over 60mg/day of B1.
I'm still fiddling around, looking for the balance right now that relieves chills (possibly the Methyl B-12 Oil alone once a day?) amounts of pain (Folate) and my endless sleep issues and IBS. I've only just begun working with L-Carnitine Fumarate. Each thing I take seems to alter the dose of whatever I've already been taking. It's such an individual mystery. Though I do find that Fred's symptoms list helps.
I did have one episode of what I believe was a-fib from the feel of it and felt it was a folate deficiency symptom. This occurred about two weeks into experimentation on the LCarn when I'd been holding my folate to about 16mg/day. After raising my folate to about 18-20mg I haven't had a recurrence of any heart issues.
Believe me, I can see that this is a sort of merry-go-round. I'm getting a little dizzy from it, but I'm trying to be patient.