I got my pouch in 1992 also. I was having trouble like yours in 2008. I had narrowing/strictures of both the inflow and outflow areas of the pouch. I needed a test called a "retrograde j-pouch study" to find out what was going on. It is a test where they put liquid up your rectum into the pouch and a little beyond and take x-rays to check the functioning of the entire pouch.
I myself had to go to Mount Sinai in NYC (a very big medical facility) where they are experts in people with Crohn's, Colitis and pouches. Sometimes you need to go to a big medical facility to really find out what is going on in certain cases.
I needed an operation to correct the strictures but before I had the operation I took Miralax to make it easier to go to the bathroom and empty my pouch. The docs had me take Miralax because it is very gentle on the digestive system but does help to move things along and out of the pouch.