Post some updates, I am doing the same thing and am interested in what you have found. I have been doing some research and have quite a list of mods to make a VR rock, but always open to suggestions.
Let's see now.
1. 22mm or larger (tough) front strut bar for stability,
2. K-mac Australia 20mm rear sway-bar, and 30mm front sway bar - this will reduce the major body roll these cars get.
3. K-Mac progressice coil-over shock/spring combos (made to any height you want) which will lower the car and offer progressive suspension which is soft initially for bumps and take-off, then stiffens up big-time for cornering etc.
4. K-Mac Panhard Rods, you'll need these if you lower the car, otherwise your back end (wheels and driveline) will slide around and thats not good,
5. DBA Gold performance cross-drilled and slotted disc rotors, these will handle the stopping of your worked car... much better performance under stress than others I've seen around.
6. Wheels - to show off your struts and rotors... - but then... you already have these, I was going with a set of AMG 17" chrome Techart-Lace (17"x8"
rims wrapped in Bridgestone Potenzza G3 225x45x17 rubbers.
7. Body kit - not much in the way of performance, but will look really nice, I particularly like the range of stores I have near me that offer gel-formed kits, and I can get a tricked up Senator front and rear bar for $720.00 in a ready to go state.
...... That takes care of the externals, now we have the other mods......
8. Maybe a 71 degree or 81 degree cooler running thermostat, will lower the tempreture at which water is allowed to flow through the engine... stock the water is very hot, and therefore doesn't really cool your engine. And heat is bad.
9. Something like an "SS Inductions" big-mouth cold air intake kit - to help you engine draw in cooler air - which will increase power.
10. Replace the stock air filter with a "wet" high flow filter like a kingdragon or K&N... a lot of people stick vortex conical filters or similar under their bonnet and remove the cold-air-box... yes they get more air... but it's hot air, and doesn't help them any. Unless you mount through a wheel arch or something, your wasting your time.
11. HSV V8 Throttle body... you can get these in the 65-80 range, while this is a bit fidly, it will improve the throttle performance/response considerably - and there will be a few kW of extra grunt added.
12. V6Supercharged heat shields, these bolt on top of your exhaust manifold and stop the exhaust heat from messing with your throttle body - because that sucks power.
13. Extractors/headers - go a set of nice formed extractors like PaceMaker or Genie - this will make a big difference.... attached to that you have....
14. A 2.5" single exhaust system. If you have a V6, go two or whatever... I have the V6 as you do... so a single 2.5" system with a hollowed or street performance cat convertor and something like a Lukey high-flow muffler.... or any brands really that allow you the cleanest simplest most direct (high flow) exhaust path.
15. Memcal... after all these mods, you need to tune your "computer" to the new parts, and possibly a new fuel octane level... without this it will try to restrict your engine to make it standard again. If your keen, add a KalMaker chip to your computer so you can whack on a laptop and re-program the thing... this way you can re-tune as you add more performance parts.
16. The big one.... the engne swap, while the above should see you hit around 160kW or so (maybe a lot more depending on parts and tuning), you can always go the supercharged engine. Imoirted like V6Supercharged.com will grab you a supercharged V6 Buick engine from America, and sell you accessores to make it haul ass.
Yes... in case your wondering... the lesser known, but much sought after Holden XU6 or Supercharged V6 uses the exact same motor.... and legally, you can bolt the thing straight into a V6 V6... fitting is difficult as you need to swap out a few yankie parts to make it work... but your looking at between 190kW and 240kW for about $5000.00 - I'd like to see a rice-boy or a HSV/FTR owner's face when your VR blows them away.....
Take care,
Murray