93 Cummins, 177K miles, auto trans.

Fresh fuel filter 10/2020.
New air filter a month ago.
All original under the hood.

This thing has lost a lot of power - labors pulling 8K lbs.

Best I can tell I am getting 15lbs. boost max. Not sure if that is good or not.

If it is, any ideas on what to look for - the service manual list a host of possible culprits, just wondering if there is something common that goes south on these that could be my issue.