Does say in the advert about no adapters I think, guess that's why its SO cheap. If you need an adapter if I were you I'd look to see id you can get a piece of 76mm alu tube (if it fits, measure it) instead of using adapters as they're too restrictive in my opinion
Well, the simple answer is yes and no to that mate.
The filter in question has a bore neck size of 76mm, a V6 has a throttle body and MAF housing size of also 76mm so when fitting adaptors it would indeed reduce it and cause a restriction.
However on a TS IIRC is around 68mm but I could be wrong, it could be smaller.
You are only limited by the same two factors again, throttle body diameter and also the diameter of the MAF housing again so fitting a reducer the same size diameter in order to fit the filter neck wouldn't actually affect it... I have found that the standard induction tubing diameter on all the models follows the same bore as these two particular items, so fitting a reducer from 76mm that matches the standard tubes wont actually cause a restriction.
However, fitting a reducer smaller for example with a different filter like 65mm neck and smaller than both items will indeed cause a bottle neck... I get exactly what you mean though B.
I have even had people ask me "What if I put the MAF in a bigger housing, can I increase the bore
of the entire induction tube to get more air in from a sport filter?"
In theory, yes you could but again if the throttle body diameter is smaller then your restriction will always be present as that is the limiting factor... But when swapping the maf sensor to a larger housing, you have to also take into account that the flow resistor it is no longer centralised inside the housing, it is sitting close to the side of the housing wall so prone to more turbulence and not getting the correct flow rate it can measure accurately.
The next option is to uprate both the throttle body to a larger diameter (ferrari F360) and also the MAF housing with the sensor now perfectly centralized somehow but that can be very costly and expensive in comparison to the gains, Then you also have to look at other limiting factors like plenum chamber or inlet variable manifold diameter behind the throttle body as the main restriction... You can go big, but the bigger you go the more expensive it gets trying to eliminate bottle necks.
The wierd thing is with Alfa's of the past 15 years is that the standard filter and induction tubing as standard is actually 300% larger than they need to be anyway so pretty good at what they do, just simply let down by poor filter housing design.
With regards to the V6 it's crazy, you get 300% more surface area on the air filter than actually required but a 3.2 ltr GTA has the same plenum capacity as a 2.5 ltr... Then with the TS's they go and restrict the hell out of the cold air feed to the box with a stupid lump of plastic known as a resonator that weighs an extra 5kg ....It's Nuts
Hope this helps