If you're still running the factory water pump, that could be an issue. The upgraded balanced flow water pump moves way more gallons per hour, something like 70 stock vs 130 on the high output? Think the '99/2000 model years and after. Only way to know what you have (unless you know what you have is stock) Is to pull the water pump and measure the impeller diameter, high output impeller diameter is 4.25" if my memory serves correctly.
Look up flowkool water pump, good upgrade/ place to start
Also what fan clutch are you running? A stock one won't cut it unless you do the spring mod, some out there sell clutches calibrated for lower temp engagement, while others on here have gone to an electronically controlled fan clutch, there's a write up on this site. Think the Hayden 2840 clutch is a good upgrade that can get the spring mod done, while the Hayden 2886 allegedly locks up sooner/ harder (never ran it myself so can't say from personal experience).
When did you last clean your oil cooler? With regards to cooling these engines every little bit helps. How new is the radiator? They are notorious for plugging up in the fins good regular maintenance is pulling the rad every few years and flushing out the fins from the back side using a garden hose.
Also a cold air intake is essential- don't know what you have but a simple filter under the hood plumbed directly into the turbo is asking for trouble. Find the K47 air box from a 97+ truck, pulls cold air from behind the passenger side headlight through the fender and through the filter into the turbo. A charge air cooler mounted between the frame rails is a good upgrade, and a better turbo will help with intake and exhaust temps. Almost any turbo is an upgrade over the factory one. I've been running the Peninsular/ Unique Diesel towing turbo for the past few years and have been very pleased with it.
It's one of the first things I fixed and then fixed, and fixed, and fixed...