I have the same problem. I'm 33 and have been on methadone for 4+yrs. It was real bad from like, 80mg to 60mg. I had to leave the room. Then it kinda went away till I got to 40mg where I am now, and my councilor won't help and has no answers other than," go see your PC". I don't have insurance and can barely pay for the methadone. I have massive gas/bloating in the evening. I thought I tried everything till I walked into the CVS next to the hospital, figuring, "if anyones going to know, it's these people". Anyways, they recomended Miralax. It's kinda expensive, about a dollar a dose, or $14.00 for 14 doses. It helped massively! I did work my way up to taking it 2x's/day, per the pharmacist,( she knows everything I'm on including methadone) and has worked wonders. If all else fails, try this. Hopefully it works.
i forgot too add that my stomach makes lots of noises too - especially when i was on treatment and shortly after - that seems to have calmed down a bit but still happens, ive broke wind about 5 times whilst making this post...thats not normal is it?