I would pull the injectors and do a pattern, leak-down, drip, and popping pressure test. Faulty injectors were a cause of a lot of the problems associated with early automotive diesels, cracked heads and broken pistons. If you're crazy, you can make your own test stand using a hand operated hydraulic pump and a 3000-5000 psi guage depending on the popping pressure. If you have a faulty injector, they are generally not difficult to service. Especially if they aren't unit injectors. The most difficult part of rebuilding injectors is mainting an extremely clean environment. Injectors use no gaskets to seal internal parts, all parts are lapped together to create tolerances so tight that 5000 psi diesel cannot leak through them. Any small piece of dirt or corrosion from finger prints could cause an injector to leak-down excessivly.