While i have been researching the intake mod for the Twin Spark i came across this very simple and informative guide, i have decided to do this myself on my 2.0TS 156 when i can eventually find the intake pipe needed
. It seems the V6 pipe is the better to use than the JTD pipe but the JTD pipe would suffice for anyone wanting to do this mod. LINK BELOW!
The mod involves taking off the 156's intake silencer / resonator and replacing it with the intake pipe pipe off of the V6 or the JTD 156 versions. These pipes bypass the Twin Sparks "silencer" with a straight through design pipe leading to potentially more Horses and a much better intake sound.
[who doesn't like that gargling burbly noise when they put their foot down
People have reported better throttle response with this mod as well as the other benefits so why not...
There is also the cone removal mod, the cone sits inside the air filter in the air box and is attached the the large air pipe that joins the MAF sensor. This has mixed results in performance/noise/throttle response but the general consensus is better high RPM pick-up but can lose lower down torque! This may benefit some engine and some not. Experiment - not all engines are the same
The most common 'better outcome' reported overall is V6/JTD intake pipe mod but leave the cone in.
Also, I personally recommend the Pipercross OEM replacement foam air filter too over the K+N - free'er flowing and no potential "filter oil all over your MAF sensor" issues people have reported.
The link to the guide - http://www.madau.net/alfa/156_V6_intake_mod.pdf
V6 & JTD intake part number: 55187325