ROB, Hi. Have a look at my signature. I use a CP_e Down pipe (DP) bolted straight to the stock exhaust. Eliminates the restrictive OEM DP. It works well. Cheapest HP you can get, gives a decent power gain, your engine will dissipate its heat better. Exhaust note is nice and purposeful, but not radical and not a cop-magnet.
I don't give CAI's a lot of credit as many people here know. I'd be hard pressed to discern a major difference on air coolness between that and an SRI that was going to be relevant. I had an SRI but that went when I fitted the CS_FMIC which comes with a real cold air ram effect through the existing bonnet scoops. CAI's are just a pain in my view. Lots of plumbing to little real advantage in day to day use. People stress over water ingestion, half the time the plumbing vibrates and cracks at the mounts, or they rattle against the tight space the pipework passes through to the old resonator void. And to my mind they are too low and are exposed to way more dust, and the pod filter is a bastard to service in its location. The SRI fits in minutes and you can see it, service it easily, and it produces a not displeasing sound. Many here will disagree with me, but I maintain my position.
Next restriction to eliminate is the convoluted stock turbo inlet. Some SRI or CAI and FMIC kits come with a new inlet pipe with all the necessary nipples on it for vacuum and BOV bypass. Otherwise just buy one as a separate item.
The Turbosmart in my view BOV is the best you will buy. Well made and versatile as it enable 100% Bypass, 50:50 and 100% VTA, is fully adjustable, and the base mount swivels so you can get it into tight spots or point the cone in the direction you want to get sound out and/or keep dust from getting into the piston assembly. I'm not sure what sound you want. More often than not, the sound is a function of the air volume being discharged and whether it is VTA or partial.
Stay away from 100% VTA unless you have a Standback to reprogram your fuel, or you will run rich mixtures, so you will get backfires, wash your cylinder walls with raw fuel, soot up your cat and potentially damage your exhaust with repeated backkfires.
CP_e Standback & PNP; CP_e 3" SS Downpipe; Corksport FMIC with Top-mount K&N filter & OEM Ram CAI; Turbosmart BOV; Dashhawk; Prosport Boost Guage; JBR solid shift bushes; DBA 4000 Wiper-Slot front rotors; Hawk Ferro-Carbon HPS Street front brake pads (@ 69,000km); Sumitomo HTRZIII's in 225/45 x 18