I have a 1997 Powerstroke that had a very similar problem. I could only make 11 psi boost with my chip cranked all the way up. Other than the low boost problem the truck ran great. Most people told me it was either an exhaust leak or a boost leak but I couldn't find any indication of either. It turned out to be a jammed up catalytic converter. The backpressure was so high that the exhaust gas velocity was not high enough to properly drive the turbo. I assume that yours has a cat on it too because it is a 1997. My truck now makes 23 psi boost. So long story short, if you haven't looked at the cat you might want to check it out. With your Auto Enginuity tool you can monitor backpressure. Stock exhaust should be around 15 psi at idle and no more than about 42 psi at WOT. Hope this helps!