What are your machine specs? Lagginess under TC changes dramatically depending on what manner of traffic you are in. If you see significant lag it's time to ratchet back the TC a bit.
By the way, Rabaul, meet lukterran, lukterran, meet Rabaul. All that stuff said about how unrealistically easy harbors are and now hokey the game is there? Just forget all about that at Rabaul. It's always an exciting time with plenty of targets if you can get to them and aggressive escorts outside. If you're not finding anything you can for sure find trouble there!
Whether that's a good thing or a bad thing changes every time you visit.
Hambone might be onto something with a mod issue.