What are you trying to achieve?
Noise?
Or getting more air in to make more power?
Basically, the standard manifold etc isn't restrictive...the head/cams are.
Even with 3mm bigger inlet/2mm bigger exhaust valves and Schrisk 268 cams, on a 2.9, the manifold (2.9) still isn't restrictive...
So if you can make 225-230 BHP and it's not holding you back....fitting bike carbs isn't going to give you anything except lots of noise and huge headache making it all work.
You can go to 276 cams with 11.5mm lift, still on hydraulic lifters, and with the biggest valves you can fit in the head (3mm in/2mm ex) and with a modified 2.9 TB still run the standard 2.9 inlet manifold and not be strangled by it.
If you are going BV Head and came with more duration than 268 and more lift than 11.4/11.5mm in order to 'need' the extra air, then you are already in big budget territory!
Personally, I'd not even think about it...if your engine doesn't need the air, leave the injection system alone.
If you want a reasonable gain, cheaply, fit a 2.9 upper inlet manifold (bigger plenum) and a 2.9 TB (if your car is OBD 1 and can take the 2.9 TB).
At no point would I even consider carbs...
