Friend of mine installs propane injection and recommends four things if you want to inject on an older PSD. 4" exhaust, cold air intake, gauges (EGT, boost, trans temp), and intercooler. You can get away with not being intercooled, but you have to be very careful to monitor exhaust temps. The system can also be set up to automatically monitor exhaust temps and reduce the amount of injection accordingly. The towing benefits are big, definitely some more umph!