Illegal upgrades are a bit of a crap shoot. The best ones are a little bit better than the best S-class mods, but they have a lower floor, so the odds of rolling a max mod are lower overall. If you are willing to grind, buying out Pirate systems and ditching the duds can leave you with some pretty boss mods. For example, the one you got there, can spawn at something like 10-8-6-9% increases (I'm not sure you can get 10% for all 4?) Illegal mods can also get you 250LY hyperdrive mods, 20% Agility, 15% damage for ship weapons...

Another vote for the Infra-knife. Don't group upgrades, put your max-stat X-class mods in the 4 supercharged slots of your fully expanded ship, wherever they appear on the grid, and you can get 55,000+ damage on an Exotic or Solar, 65k+ on a Fighter.