Go with cams and head build up.
The stock bottom end will handle it, and Im pretty sure the Stock ECU will also handle it. (the only thing you might ever need to change is the redline, the stock ECU will handle fuel etc easily)
Pull the fuel rail off, unless you like the looks, it does nothing for your performance, unless you want to start making more than about 300hp.
As a cheaper alternative some ITR or CTR cams will fit, and give you nice power boost. no need to change retainers etc either.
and a Time of 15.01 is awsome!!!!!!!!!!
Iv always wondered what they were capable of, and with my extra 10hp I feel with the right technique high 14s could be possible from my car.
Its good so see an actual number for an SiR.
With Skunk 2s and some time on a dyno to set the cam timing you should be well into the mid-low 14s.
And you will be able to do it when ever you want, even on the street when some fool in a VW VR6 trys to pass you.
With NOS you will also be in the 14s, maybe 13s, but at a huge expense. Engine life will suffer, and you will only be able to do it when the bottle is full, and then only for a short period of time. Great for the track, but thats it.