I dunno.
In my experience, nothing measurably potentiated methadone for me. And I tried everything. But methadone was a black hole for me. At one point I was taking 240mg in the morning followed by 140mg in the late afternoon, a total of 380mg. Even still, every morning I woke up in mild withdrawal, feel cold and unwell etc.
I even tried stuff that is known to actually work well, like fluvoxamine (works so well it's been associated with methadone overdose, but likely only in old or ill individuals not used to methadone). So even with fluvoxamine and a nearly 400mg a day of methadone dose, I still didn't feel 24/7 coverage. I did feel the methadone while it was working, I remember my afternoon naps were quite glorious. And I could enjoy eating food (not a fan of food) and watching stupid TV shows like a normal human being. Even got a little fat for a while. I became a true American.
But the dream didn't last forever, i eventually got off of methadone (to my methadone's clinic shock -- I had 100% take homes, didnt tell them I was tapering, saved the pills, and one day walked in and said I was done). I lost my new found appreciation for eating food and watching TV. But it was interesting to experience. Food never tasted so good ever in my life. And I could sit down, calm and relaxed, watching dumb TV shows etc. I was at peace, in a way. But I simultaneously realized it was a very bad thing, a dead-end road.
I miss methadone sometimes. Even recreationally, these days I would 30mg of oral methadone over any opioid. Even say IV oxymorphone. I like the duration, and the itchiness.