I know a part of it was the air intake box.
See this thread.
987 v 986 Air box
Also take a look at this thread.
http://986forum.com/forums/general-discussions/31693-maf-throttle-body-diameter.html
I've got my 987 air intake box modding done, using the stock MAF house so the computer can read the air flow correctly. If you use the larger MAF house you will need a tune.
I also went with the 76mm 996 Throttle Body and the 997 Distribution T to the Plenums.
Hope to have it all installed in the next couple weeks. Still waiting on some attachment parts to come in.