Engine mods:

Basically it is still running the standard 1.5L SOHC Alpha block and internals, though it has been toughened up somewhat thanks to a turbo kit from ChipTorque in Queensland and installed by SAS here in Sydney.
This kit has been around for sometime and is emissions safe and reliability proven. Because the kit has been around for a while and because my car was a special case (being auto and all) it did require a few custom touches.
For example, the standard T2 Garrett turbo was replaced with a GT25 roller-bearing item, which allows for faster spool-up times. A custom oil catch can was also welded up and looks very trick and the standard ECU was replaced with a later-model item before being remapped. This also meant that the stock MAF sensor was also replaced with a MAP for easier tunability. It also means that I can run an atmospheric BOV with no dramas.
Apart from this the kit was set to around 5psi, which is fairly low considering. A K&N pod filter is mounted low out of view and the BOV is a plastic recirculating item as found on factory Porsches. The intercooler is also an air-to-air front-mounted Garrett piece and is a little smaller than what most people would expect from an aftermarket cooler, but it does lend itself to that stealthy look.
I have just switched all the piping over to stainless, so the kit is now ready for a boost increase. I am also running a Turbosmart Type 1 BOV.
Earlier on, when the Excel was still in NA form, I made some minor modifications like changing the throttle body from a 41mm bore to a 48mm (which remains), changing the headers to 4-2-1 and installing a carbon-fibre cold-air intake.
This last mod not only looked awesome but it really did provide a suitable gain and I would strongly suggest people looking for easy power check it out.
The exhaust has just been upgraded to a 2.5in mandrel-bent system and I must say the difference is huge. The car now pulls extremely hard to start to finish. Awesome.
So then, whats it like to drive. Well, packing almost twice the power of a factory X3, the torque is the most noticeable improvement. Basically, it drives like a standard Excel until about 3000rpm, when the boost kicks in and you really start to get hurtled forward. It you slam the throttle down, there is a one second lag before the boost kicks in the thing just takes off, torque steer and all. You especially notice the turbo on hills, where it now just floats up and on highway cruising, where it seems at its happiest.
I also just had trans strengthed in prep for more boost, plus I had a high-stall converter and a transmission cooler added for kicks.