[Bfan]

If we are looking at 986 S 3.2 you have two options with this airbox.
1. Saw the original MAF tube off the original airbox and plumb it ont the new airbox or

Use a MAF tube for 987 airbox that can take the original MAF and
2. a) Remap the ECU with tune from a P-car with the same diameter MAF tube and the same type of computer (i.e. 996 from the same model year for the most part but you might want to research this further) or
2. b) get a remap from some tuner with good reputation that knows what he is doing.

I myself have chosen to go with alternative 2 a) and got the so called rest of world tune from a 01 996 on my Box 01S. That way I got rid of the eternal CEL that I had for two years after catless performance header install. I first tried to move the downstream O2 sensors by lengthening the wires with thick wires to no avail, then tried so called O2 simulators but they did not work either. A good tuner would do the same but I like to be in some kind of control over what is in my car and also the original Porsche remap is much cheaper than a complete professional remap.
And there is no question about it; these engines can use the improved breathing, but I think you should do both the intake and exhaust at the same time. Hope this helps.