Honestly, there are better things you can do for sound and BHP, I did so much research on it several years ago and finally came to the same conclution as most , you cannot beat the porsche air box for true cold air induction , So Based on that I started to explore the Porsche options which seemed to be fit an X51 airbox £2k
or £1200 used if you can find one , fit a gen2 airbox £300 theory was it was duel feed like the gen1 X51 so that would mean more cold air in . anyway personally I fitted an aerokit rear wing this meant the air intakes were forward facing not rear facing like on the OE engine cover this would create more of a ram air effect even better if you add the gt3 intake scoops.
I then found my existing gen1 airbox was more than capable of handling the air flow and the stock paper filter was the bottleneck along with the fact that the resinator box on the gen1 is plastic welded in unlike the 996 which is screwed in and can be easily removed, So I fitted a BMC air filter and silicon hose with resinator cap , had I been handy DIY I would have dremmeled off the resinator box as this would free up 30% more of the airfilter thus handling more cold air , if you do this the resinator cap with the silicon hose becomes a resinator plug.
So you have now spent about £100, with the other £500 that the fabspeed thing costs go and buy yourself some 200 cell cats. this will give you far more sound and BHP than the fabspeed airbox , and if you like a pretty carbon look in the engine bay then get the top of your airbox carbon dipped which is what I did. you wont need a remap with 200cell cats and it will pass MOTs no problem
then the next thing should be GT3 throttle body and plenum and sports back boxes if you havent got PSE you will need a remap with the throttle body but you will be getting max cold air in and max exit gas out without getting into really serious money.
Hope my thoughts and what I did help . :thumb: