rpms quiz

Looking for more theories on the symptoms in my 2QM20. I occasionally have a dip in rpm's or throttle when under way. It never gets worse once the symptoms have occurred and I have noticed the last couple of years. This year, I've changed out the fuel lift pump and have fresh, clean fuel and filters. I have no fuel leaks. The head and one cylinder was rebuilt in 2006. I have minimal white/grey smoke, which get more intense under high rpms/load. I use FPPF in my fuel. run a 3-blade feathering kiwi prop.

So, might I have a small pin hole air leak somewhere (where?) that "goes away" once engine heats up? I've checked the fuel tank pick up tube and there are no cracks and the screen is clean. could a cranky blade on my prop alter rpms like this? It feels like a short fuel shortage, but the problem never gets worse.. driving me crazy trying to diagnose.
thanks for the ideas.

The best things about diesels is that even the seemingly most complex issues always prove themselves out to be a basic malfunction of the operating principles. After many iterations of troubleshooting, I discovered the hose clamp on the fuel line feed from my fuel tank was partially loose---I was able to tighten it 3-4 more turns. Hard to believe this could have let enough air into the feed to create the symptoms I experienced, but since I made this adjustment, the issue has gone away (knock wood 2x). Have faith in your trusty diesel engine...