I have a friend who has major stomach problems. It is a medical condition, so he works around it. Anyway, most protein powders gave him gas. I happened to have a few different brands on hand so I gave him a sampling to see the reactions.
First I gave him MetRx, which made him very gassy. The Dorian Yates protein gave him less gas. The EAS gave him no upset what so ever. I believe in a mixture of fast and slow absorbing proteins, so as we discuss, none are just a whey or soy of milk, etc. But as you can see, different brands resulted in different gas levels. You may have to try a different brand.