Hi
The following parts should get you about 35 extra horses:
-997 T plenum, $ 63.50 on Pelican
-Throttle Body Seal $10
-74 mm 996 throttle body, About $ 150 on Evilbay
-Aftermarket headers About $ 250
-Desnorkel (do a search on that) Cost: free
Total about $ 473 or roughly $ 13:50 for each HP
You can easily use the original rubber boots for T plenum by stretching them. Some of this might be illegal or make car fail smog test were U live. The headers will cause cheque engine light, but you can cure that with aftermarket downstream Oxygen sensor simulators, costing roughly $ 150 for a pair.
Next step in IMO would be
-Cayman / 987 air box, about $ 200 on Evilbay
-Cayman / 987 MAF housing and reflasch of the DME about $ 800-1000
If U do all above, it should net close to 300 hourses. After that we begin to talk of real $$$ for more power.
Regarding forced induction, Porsche guru/specialist Jake Raby does not recommend it for this engine.
More good info in these threads on another forum: see
here and
here
Good luck and keep the rubber side down