Hi, I'm not familiar with that particular model of Volvo. Since you posted in the IDI forums, I'm going to assume its one of the older VW 2.4L inline-6 engines. In that case, practically everything you can do to the 4-cylinders, you can do to the 5 and 6-cylinders. The first few things you could do are turn up the fuel on the pump, fiddle with the wastegate on the turbo for more boost, and add an intercooler. Of course, you could also modify the governor in the pump for more high-end power, add bigger nozzles, and a free-flow exhaust. It would be wise to add boost and EGT gauges as well.