I finally got a chance to drive my newly-turboed 7.3 IDI on the highway. I had been seeing 5-6 psi boost on the bumpy dirt roads, and figured once I did some fast runs it would make more. Pump turned up two flats, but it's of unknown age, as are the injectors (odometer has 189k but I think it's been swapped). It starts fine, hot or cold. But it won't make over 5.5 psi at all, even up to 3000 rpm in fourth and fifth gears (4.10 rear) with the pedal on the floor. Pyro was just under 900F during the wide-open runs. About 40F ambient. No load in the bed. Didn't see any smoke but the rain would make it hard to see a light haze. I don't hear any obvious boost leaks. Due to rain I have not checked to see if the wastegate is sticking open. What should I be thinking of first - boost leak, wastegate or turbo problems, or simply not enough fuel from old pump/injectors?