To properly maximize gains from building internals and/or changing compression...you need a new ECU. To get any appreciable power at all...you need a new ECU. So you need a little under $3k to buy it, you'll need someone familiar with it to help you wire it for at least another $1k, then you need a tuner who has done it before and lots of hours on a dyno....and now we're at $5k on top of the cost of new internals and the labor to swap them. And you still wont be making as much power as an NA S54 with cams and headers, you wont have VANOS anymore, and your motor will need a rebuild it otherwise wouldnt.
Get cams and headers and generic software. If that isn't enough power for you, you need a new motor/car.