If you want 150hp out of your motor, hook up NOS. That's the only way you will get that power on the cheap.
+1 NOS
At the end of the day, with all the possible mods you could do, it is still going to be a N/A and you will only end up wanting more power.
I understand where your head is at, I think we all do, but the bottom line is....
You have youth on your side and a great little suby. With a bit of basic maintenance & TLC will be a good reliable car that will serve you well whilst on your P's. Save the bucks for later on mate. If there was a cheap easy way to get 150kw out of a N/A lots of people would be driving around with those figures.
Just take a break from thinking of the possibilities and take a look at the big picture.
It's ok to just want more but you ARE flogging a horse that died a long time ago.
Not being mean mate. It's just the way it is and you would be doing your self a favour if you could accept this.