I think when I was younger and first started doing psychs I didn't have nearly as many problems as I do now. I'm still only 26 but in 10 years I guess I have become more sensitive to pretty much all of them, at least in terms of how my stomach can handle them.
These days my diet is mostly whey protein. I got a big chunk of cid months ago and have had a terrible time with taking high doses and having gas bubbles form in my stomach and just sit there for 30 minutes-1 hour generally a few hours into the trip, around the peak.
It's weird my stomach will just start to rumble and then bubble a bit and BAM I'm hit with agonizing cramp-like pain that only recedes after I can push it out. Weird, but I never had this with acid in years past. I did used to get heartburn from it, but never the gas issue. I am thinking it could be linked to whey protein though because I usually would have a shake early in the day before not eating a few hours then dosing.
I've also had similar problems with 2CE about 3-4 years ago. 2CE oral wrecked havoc on my stomach, but not the painful gas bubbles. Just rumbling and lots of time on the toilet. =(
I still question though if it is really a diet issue or maybe just more of a high dose or sensitivity issue. I was doing molly like crazy 1-2 years ago and started off doing all oral. After a month or two of that I couldn't tolerate it anymore, not bodyload just gagging and puking after swallowing a pill capsule.
So then I started doing molly plug, and well yea it will clean me out real fast, but I can handle that (actually I like having a psych do that in one sense because it helps keep my weight down - I am very low body fat but gain weight easy due to type 1 diabetes).
Now I pretty much plug anything I can, which helps a lot, but for acid isn't the best. Actually I did try acid blotter plug followed by a rinse with some water and while the trip seemed to be weaker than what oral would have done, I still had to eat a lot of antacids to keep my stomach in check that night. So it's not perfect.
I get bodyload-type stuff sometimes too, when I combine a lot of psychs at festivals and stand for hours especially. I'll end up having back pain by the end of the night but really I think that's just from the experience. I've had back pain at home from psychs too but usually it is just because I'll sit in a bad spot for a few hours, distracted by the drugs, and end up stressing the muscle.
I am thinking the next time I do acid I will just cut whey protein the whole day and stick to fresh fruit. I also had some of the stomach gas issue after doing 2CD plug and M1 oral/later plug but not until late in the night when I decided to drink a protein shake LOL. A few minutes later and I was lying on the ground like "fuck I shouldn't have tried to eat."
Of course the other option would be that it is tied to a supplement I take frequently, possibly piracetam but I doubt it. I mostly think it is sensitivity and the protein... but it could just as well be any food, I just favor whey shakes so heavily. I never had trouble with whey on MDMA though by comparison. I would always have whey at the end of the night after doing tons of molly, and this was my life for every weekend for over a year.
I was thinking to try taking those papaya enzyme "chewable pills" and see if that helps. The issue for me is really finding a way to get the stomach to sit still during all the serotonergic stimulation.