987 v 986 Air box

[berty987]

A quick search through the parts catalogue suggests the only difference between a standard 986 and the 550 aniversary is the air cleaner housing and the MAF , the rest of the inlet system , engine and body (save trim parts) remains the same. The 987 MAF is supplied complete with the housing which bolts directly onto the air cleaner , the connecting pipe to the throttle body is standard , there is no reason for it to be different as the TB is the same 68mm unit on the 986 as it is on the 987 3.2. The flexible boot used on the 987 to connect MAF to the throttle body (its located futher back from the inlet manifold due to the split intake plenum after the throttle body) is the same part on the 68mm throttle body as the later 76mm unit found on the 3.4 (it just stretches slightly more). I am therefore surprised that if the 986 and the 550 are essentially the same body, chassis and engine why does the 987 air cleaner need modifying ? Is the 550 shell modified during assembly ?