I have a 1994 ford powerstroke diesel 7.3 L. While accelerating the rmps will unexpectantly drop for a few seconds and then return to normal for a few minutes before doing it again. I have changed the fuel filter and cleaned the air filter. I am looking for any suggestions as to what may be causing this problem.

Ensure engine oil and filter have been recently changed. Check engine oil level and oil pressure, preferably with a mechanical gauge, which affects fuel. The link below may help:

https://www.askmehelpdesk.com/cars-trucks/faq-how-troubleshoot-repair-maintain-hondas-selected-other-vehicles-46563-8.html#post1415281

Disconnect your exhaust sounds like it is plugged