Well, by a lot more, relative to the actual engine power kinda. The biggest thing is exhaust, you'll want to put a 4 in pipe, straight will get it less resistance, but I've heard in the suburbans, it can be quite loud in the cabin. If you want it relatively quite, you can get muffler kits, don't know how they work. Air intake I've heard that you can butcher the stock box and get a lot better flow, I personally get the S&B cold air for $270, but probably shouldn't have done that. Just open up the intake and put a K&N cone on it, lots of people get 97+ intakes and put them on, those will provide sufficient air. DO NOT buy "marine 40HP" injectors, I've seen where people don't gain power from them and they are just a scam. Heath Diesel is a good place to look for the performance mods, he's the guy with the land racer, or at least he has the fastest 6.5 diesel recorded. Heath Diesel also sell performance chips, the two options are 40 hp and (80-95) ft/lbs, and 80 hp and 160 ft/lbs. Rear wheel gains are roughly 30 hp and 60 hp, so good gains. Lots of people get a TurboMaster from Heath diesel, for a 94 you should be able to make your own, a link is at the end. This allows you to control the amount of boost, but there is a 2 mpg loss with it, if you do this keep boost under 15 psi, that's about all the engine can safely handle. That's about all you really can do without completely changing everything. I've seen some of these cranking 300 hp but there was also a lot of money put into them, almost enough to just go buy a D-Max.
On another note, you might want to make a manual override for the glow plugs if you live in a colder environment. My dad and I did it in an hour, and we didn't know what we were doing. Mine is a 96 so its setup different than yours. But this is what we did for mine (there is a youtube video with a 95 I think is the same as a 94), go behind the engine cover and there should be the glow plug relay and there are 3 wires running to the little clip on the back of the relay, real tiny wires. They are hot, ground and one's just a signal wire. Anyways, cut the hot and signal wires and just run a switch to it. If you do this, get self regulating glow plugs, AC 60g and Bosch Duraterms 80034 are both, I got the duraterms and cold weather isn't an issue anymore (I live in Butte, MT). This does set off a trouble code, my dad fixed that, he's good with electronics, took a course with them though the Army. I think he ran a diode on the yellow wire (signal) to a 12 volt hot. This will make the factory glow time come on and the switch will let you keep them on a little longer.
If you really want power, buy lower compression pistons (17.5:1) I've seen, currently 21:1 compression and get a holset Hx-35 turbo from a cummins, the lower compression lets you safely run higher boost levels and the Hx-35 is capable of 50 psi, as opposed to the 7 psi max from the stock turbo. You'll get higher boost with the engine at higher rpms, but you'll have a little lag at the lower one's, I've seen somewhere that someone got 353 HP and 650 ft/lbs of torque doing this.
Heres the links:
TurboMaster - DIY Turbo Master
95 Manual glow control -