Assuming your ottomind is working and you don't have a boost leak, you can increase your boost by shortening your wastegate actuator arm. I think each complete turn is good for around 3 pounds increase or decrease if you lengthen the shaft. Or you could install a boost elbow. To check for the first two issues, you might want to just block your wastegate line to see what kind of boost you can get. If it stays at 26, then I'd say you have air or fuel problems.
Also, how high can you get your EGT gauge to read at 26#'s?
Dan