Hey mate. Welcome to the forums.
If you were after a bunch of power to begin with, you were probably better off going with the XR5 Turbo to start.
But since you have already purchased, think about putting a turbo in aftermarket. There's a bunch of guys in Queensland (can't remember exactly what they were called), but they have photos on the forums here somewhere about them dropping a turbo in an LS LX.
With the turbo, obviously you'll need to do exhaust, intake and
ECU tune. With all that you should be thinking about 200kw.
Even if you could stroke the 2L duratec, I wouldn't think it would pull all that much extra power anyway. Definitely going to need forced induction for greater power gains.
And another simple way to get faster, remove weight!!! Take out as much as you can that you don't need...