* Open saved files. Go 2 your last saved game folder. 
  (they are in order of which one was saved first.)
* Open "game.sii" with notepad. Search for such file: U must familiarise yourself
  with the engine you have in your truck so you can recognize it on the page.

Look for on the page "vehicle_engine_accessory : namless
torque:600 "or which ever engine is yours"
front_wheel_engine: false

So on and so on down to where it says:

info[0]: "@@ui_engine_hp@@:[align hstyle=right]600 hp [448 kw] @1800[/align]"
info[1]: "@@ui_engine_torque@@:[align hstyle=right]1650 lb. ft. [2235 N.m] @1200[/align]"

Now change this:

below vehicle_engine_accessory
from 600-1000

and down farther 600 hp [448 kw] to 1000 hp [747 kw]
and 1650 lb. ft. [2235 N.m] to 3000 lb. ft. [4065 N.m]

I forgot to mension that the horse power increas will not accurally show on the listings 
of the motor but u can tell when u r driving the truck.