don't pin me down on this but I think you either edit the thrusters max-speed... yeah that sounds right... thrusters are in st_equip.ini...

or you can just edit you own ships' speed in the engine.. engine_equip.ini

best way to do it is to make a new thruster so that npc's who happen to have the same one as you don't put the pedal to the medal and crash into things...

oh and the thrusters that are in the game now have a speed or rather the power to do 120 add that to the engine's 80 and you have 200... be sure that when you edit either the engine or the thruster that you have to add the two to make you top speed. The rate of acceleration is depandant on the mass of your ship though..

hope that helped.