I'd suggest getting some decats that have the brackets on them (such as Berks) for securing them to the oem support. Alternatively you could get some brackets made up and welded on to your current decats.
You won't get any extra power from an after market back box or mid pipe. There are some gains to be had from an uprated y pipe and/or race cats/de-cats but that would still need a tune afterwards to get the most from them.
As you say you need to find out which part is affected first. If you want to stay oem then He has most things much cheaper than Nissan prices.
I'd take it straight back to the dealer and explain that the car has a malfunction light on since it's been serviced and see what they say. Hopefully they will do a diagnostic and be able to tell you what the fault code is which should shed some light as to whether it's related to the work they did or not.
Not really sure what the technical differences are, but I know it works! I think it's machined slightly differently to even out the air flow to the front two cylinders which seem to be slightly restricted in stock form. Abbey are the guys to speak to on this for a better explanation
To get the torque gains on a 296 facelift car you really need a plenum spacer and an MREV2. My midrange increased by about 30 lbs/ft after a tune with these mods.
Nice result. As you say it's more about improving the overall feel and drivability than top end numbers with NA tuning. Decats or high flow cats and an after market y pipe will yield further gains and should see you through the 300 barrier.
I got my carbon one from EP Racing, a trader on here http://www.epracing.co.uk/Carbon-Accessories/Nissan/350Z/350Z-Carbon-Cooling-Panel/p-75-122-123-1448/
Quality and fit was very good.
Have you thought about getting something custom made? I'm sure someone like Powerflow could copy the design and you could choose how you want it to sound. I'd imagine it would be cheaper too.
I have that combination. It made the engine have a slightly deeper tone, only slightly though. Overall volume I would say is about the same. If you want more noise I'd go for a y pipe and high flow/decats. They will make much more of a difference to the sound.
I can't really see how a Y pipe would remove the cats? The Y pipe shown above would just mate up to whatever cats happen to be fitted wouldn't it, whether they are de-cats, high flow cats or standard?
I've used Manchester Car Refurb myself and their work is excellent, but not had a body kit fitted. Can't see any reason why they wouldn't though. Just give them a call and ask.
I'd just buy the oil and fluids needed and supply them to the garage doing the service. That way you know your getting decent stuff put in and it will be recorded on the service sheet as being done.
I'm thinking about ordering some nice bolts for the engine bay from here http://www.tastynuts.com/ but I don't have a list of the necessary sizes. Does anyone have such a list that also tells you which size bolts go where?
For the moment I'm not going to change the plenum bolts or the strut bar bolts.