Was curious so I searched Wikipedia for FQ400,
"In the United Kingdom, many special Evolutions were introduced, including the FQ300, FQ320, FQ340, and FQ400 variants. They came with 305, 325, 345, and 405 hp (227, 239, 254 and 298 kW), respectively. Although Mitsubishi have not confirmed the fact, it is widely rumoured that the FQ stands for "f**king quick"
Apart from that I have nothing else to add to this thread.