first off, un-screw ever screw and clip on the top & underside of the std splitter (see red circles)

then everything pretty much comes off then first re-attach the splitter to the underside of the bonnet
As youll probably notice the aftermarket splitter has its own scoop in the front to channel the air evenly over the entire core (results later)

First things first, the scoop comes unpainted and says to trial fit before painting to obviously make sure things are ok, mine fit without a problem.. so hes the product unpainted:

Trial fit:

Photoshop compare of the two items.. you can see its quite a bit larger both tall and internally, it scoops further forward on the bonnet.

Next it was painted through BoostedS15 and re-fit..

The next couple of pictures are just misc shots of the two products fitted.

Stupid me forgot to take more photos, but wat eventuated was, u put the new thermostat into the engine. Attatch the self adhesive gasket to the thermostat housing. Then you attach the housing so it looks like this.

The results? well using my scientific testing tool below ($50 at dick smith) I stuck the external probe to the underside of the intercooler before and after fitting the products, before fitting the intercooler would maintain (whilst moving) a constant 2 degrees below ambient tempreture e.g ambient 25, cooler 23.. after fitting it dropped to 4-5 degrees below ambient, not much of a gain you might think, but the main improvement was when stationary the cooler would heat up to nearly 20-25 degrees ABOVE ambient this remained unchanged before and after fitting, however after fitting the scoop and splitter the time it took to re-cool the i/c was nearly 45% faster then the standard scoop and splitter (2 minutes 35 seconds) the cooler also suffers a lot less from boosting tempreature increases (i.e heats up while flowing high boost)

Tests are not exactly scientific but the results I experienced are pretty noticable in my opinions so worth the money spent (about $500) when I spoke (read wrote) about the time it took to re-cool the cooler the test I used was stop ---> accelorate normally to 100kph and maintain constant speed till tempreature returned to below ambient temp.
If youve got any questions don be affraid to ask...
Once again, I take no responsibility by any damage that may occur to your car by fitting any of the above products, what works for one may not work for others, best to contact a professional whenever modifying your vehicle.