What to do to upgrade the 2.5TD and the 3.0TD engines from Mercedes?

What can i do to upgrade this engine, apart working the injection and the turbo ? i want the max performance i can get from those engines.

thanks!

The Engines are the dated 1993, the 2.5TD has 126bhp and 230Nm and the 3.0TD has 147bhp and 280Nm. No electronics