Well . . . skepticism is a good thing! Never lose it.
It appears that I do owe people a bit of an apology for my first post. You see, I only recently began exploring the CIC. (Impressive database.) I knew there was a "Cheats" section, but had yet to look through it. After reading your comments today though, I did so. To my surprise (and chagrin), there's nothing listed for Privateer. Sorry for leaping before looking, but I've always assumed the Steltek "trick" is pretty much old news and well-known, especially since Origin has known about it for years, even before Privateer 2 was released (and possibly as early as the release of Righteous Fire.)
Anyway . . . happy to make amends.
It's a good question whether the procedure I outline below is a cheat. On the one hand, you can argue it is, because once you've reached the end of all the missions in Privateer (playing them out as the game "intends") you receive only the one Steltek gun. On the other hand, you can argue it isn't, because no playtesters' codes are involved, nor is any invasive programming (as I understand the charge of "editing"). In fact, you use only the technology that the games (particularly Righteous Fire) openly offer, and you even have to buy (yes, fork over hard-earned credits for) each new Steltek gun you want.
Rationalizations are easy too. That you apparently are allowed only one Steltek gun grates on common sense (and is probably the most frequent gripe about the game). I mean, come on! Resourceful privateer that you are, you can't find an "ally" who's willing to duplicate this new technology for you in the year before Menesche steals it and does so for himself? And what about those visits to Perry? It's 2669, a dire year in the war, and you land on a military base with an unknown weapon sticking out like a sore thumb but no one is the least curious? (Why, Confed should have been all over that gun, with or without your knowledge, and then in short order produced its own version. (Hint.))
To be clear: In Privateer, you can have as many Steltek guns (boosted and/or non-boosted) as your chosen ship has gun slots. (You can also have one or more Steltek guns on your ship in Righteous Fire up to, but NOT including, the ship's maximum number. (But you probably won't want to.) More on this later.) To add Steltek guns, you need two things--the game Righteous Fire (RF) and 100,000 credits for each new gun.
Basically, you can add one or more Stelteks to your ship in Privateer at any time during the game (provided you have the credits), and whether or not you have gotten to Delta Prime yet (or ever go). Understand however, that if you do so before going to Delta Prime, the Steltek Drone (true to its diehard nature) will make its entrance all the same and dog you at random until you destroy it in the ordinary course. (Still, having the Drone on your tail from "Tayla" through "Taryn" might enliven the old game and appeal to some. I haven't run that gamut myself.)
The procedure is ridiculously simple (though there are a few "rules" to keep in mind). The key is to realize that the software engines for Privateer and RF are almost identical (and understandably so). In this regard, it's no coincidence there are nine different guns in Privateer (including the Steltek) and also nine in RF (where the Fusion Cannon has "replaced" the Steltek). That's right, you guessed it--the code for the Fusion in RF automatically translates into the code for the Steltek (non-boosted) in Privateer.
So . . . choose a saved game from Privateer (preferably the one at Perry where you're about to go off to destroy the Drone, but IN ALL EVENTS one that is on a planet or base with a ship dealer), and then in either DOS or Windows rename the file's extension from ".sav" (Privateer's format) to ".prs" (RF's format). Run RF and load the saved game. (BTW, while you're in RF, DO NOT fly your ship or when you try to land, you'll crash (the game, that is), which is why you must have a ship dealer at hand from the start.) Go to the ship dealer and buy as few or as many Fusion Cannons as you want and can afford and your ship can take. Also feel free to buy Isometal Armor and the Advanced Repair Droid, but DO NOT buy the "gun cooler" or any of the "enhancement" modules for engines, thrusters, or shields. If you're using a Tarsus, Centurion, or Galaxy, feel free to buy the highest "Levels" of engines/shields offered, but if you're using an Orion, DO NOT buy Level 6 or 7 engines/shields. These "no-no" technologies are not compatible with Privateer, and though you'll be able to lift off with them, the game will crash when you try to land. (FYI, the only downside to buying Isometal is that if it becomes damaged, you must return to RF to repair it.)
Your buying-spree ended (at least for now), reverse course. Save the game in the normal fashion and exit RF. Rename the file's extension from ".prs" to ".sav". Run Privateer and load the saved game. You'll find that each Fusion Cannon is now a Steltek gun (non-boosted). When you finally meet up with the Steltek, all the guns get boosted (the Steltek are such a generous race). If you add any new guns after your encounter with the Steltek, those will be, and will remain, non-boosted.
As mentioned earlier, you can also have one or more Steltek guns on your ship in RF (thus preserving your pride against the spoiler Menesche). Simply choose a saved game from Privateer that has at least TWO BOOSTED Stelteks, then run RF and load the file through RF's transfer program (activated when you select "NEW"). The transfer program will, true to script, remove one of the Stelteks, but only one, leaving the other(s). (Any non-boosted Steltek guns on the ship will automatically become Fusion Cannons.) If you want to remove any or all of the remaining (boosted) Steltek guns (and you might), then you must save the game in the normal fashion, exit RF, rename the file's extension from ".prs" to ".sav", and run RF and its transfer program again, repeating this process for each successive gun you want removed.
Why would you want to get rid of most, if not all, of your Stelteks in RF? Because RF (favoring the Fusion Cannon) doesn't know what to do with a "tenth" type of gun, so it defaults it to the power of a mere Laser, and even a bit weaker than that. (It really does become, in Wedge009's original estimation, a "plot device".)
Sorry for the length of this post, but I guess the info is overdue. Hope people have some fun with this new dimension to Privateer.