987 Airbox and 74mm TB: MAF and tune issue

[The Radium King]

yeah, i changed for two reasons:

- the 987 holder is larger, so you avoid the bottleneck. with the 986 holder the diameter decreases as it passes though the holder, then increases again, so you are doing work (compressing/accelerating air) for no reason.

- i wanted to see how the 996 tune worked on my car. i am of the opinion that porsche depowered the 986 engines so as to not compete too aggressively with the 996. a quick ratio analysis shows that the 986 3.2 makes less hp/litre than the 996 3.4. given that the two engines have the same bottom end, heads, etc., the only place porsche could throttle-down the 3.2 was exhaust, intake, and tune (fuel, timing). i made it my mission to transfer as many oem 996 parts onto my 3.2 as possible to try and gain some of that hp back. for exhaust i used the chinese stuff (fabspeed clone) and intake is discussed in this thread. 996 tune was the last piece of the puzzle.

regarding adapting the 986 holder to the 987 airbox, the best work i've seen was done by kram on this forum, who has posted images of his work. me, i sawed it off, pulled the airflow straightener off a similarly sized bmw maf holder and glued it in, and used a silicone reducing coupler to join it to the airbox (from siliconeintakes.com, but available on ebay i'm sure). with the coupler, the small end was sized to fit over the maf older, while the large end was sized to sleeve inside the flange on the airbox (i wanted to leave the flange on the airbox so that i could use a 987 holder in the future). i can send a pic, as i have the old tube just laying around at this point. note also that BMW makes a maf holder that is about the same diameter as the oem holder, takes the oem maf, and *i think* mates to the 987 airbox (can't recall, but can check when i get home if you like) - i didn't use it as the ID was not a 100% match to the original but is most likely close enough.