There are a ton of things you can do to simply out pull, out drag or simply out run virtually any gas engine.
I have an 89 Cummins. My older Cummins has two distinct disadvantages compared to your newer Cummins. First I don't have an intercooler, however thats no big deal because I can find an intercooler at any big rig salvage yard or shop for small beans.
I also have the VE fuel injection pump, which is basically a distributor which instead of delivering an electric current to spark plugs, delivers fuel to each injector. The VE pump is also capable of timing the fuel delivery at a given RPM, like any typical distributor. Power increases are done by the turn of a screwdriver, but the pump is physically limited by design as to how much fuel it can deliver. Unfortunately it's very expensive to swap out the VE pump for the better P-pump. But I can still still double the horsepower and increase torque to over 700lb, even with the VE pump
Your Cummins has an inline pump called the P7100. (P-pump) It's capable of delivering much more fuel because it has 6 plungers pumping fuel to each injector, unlike the VE which only has one and distributes the fuel to each injector. Cam plates or torque plates allow the plungers to pump more fuel.
Having more fuel delivered to the injectors is useless without big injectors to spray in all the extra fuel into the engine. Injectors are available thru various diesel performance shops.
Once you can deliver more fuel, you need to cram in more air to make power. Turbo modifications are the next step. My Turbo on my 89 Cummins uses a big 18cm turbo housing. This housing is too big and causes alot of turbo lag. To drop lag and increase the pressure, I'll be switching to a smaller 16cm housing. In your case you have a small and restrictive 12cm housing, therefore you should consider a larger 16cm housing.
Other than replacing the housing, for really big power gains you can swap entire turbos with high pressure units such as a Holset HX-40 or go with twins. However once you're pushing more pressure, you'll really need to "O" ring the block.
Anything you put into an engine must come out. A large diameter exaust pipe allows reduced back pressure and lower EGTs
Finally it's recommended you install a pyro gauge to keep an eye on the exaust gas tempatures. Diesels can make alot of heat in short order. The pistons are made of aluminum and will begin to melt at around 1300 degrees.
Ed
