I had to take my 07 Cayman in for service because it threw a code P2402 indicating Evap Emission Leak. Something to do with the canister. Had this same issue when I had a Boxster.
While in the shop my mechanic noticed my battery leaked and the positive cable was just about gone. I had to search for part number 997.612.993. 00. Come to find out that part is discontinued and the replacement part in the Porsche catalog *(997.612.90801) will not work it comes too short. The original part cannot be found anywhere in the area. All the dealers I called were all scratching their head on why the new part will not work. Long story short my mechanic sent me to a Porsche dismantler where one was found. All told, a real nightmare. The savior in all this is my trustworthy independent mechanic!
I had to deal with a kind of similar issue recently. My 2007 Cayman wouldn't start even though AAA tested my battery and indicated that it was good (they even attempted to start the car using a freshly charged booster/power pack, but to no avail). Got the car towed to the shop and they determined that the starter was good but a cable from the battery (they called it a "distribution" cable) to the starter was deteriorated along with the connecting pin. The shop had the pin but not the cable, which they ordered from a dealer that was over 2400 miles away.
Yeah I heard from a few others experiencing this. The shocking thing about it all is the unavailability of that harness, parts or replacement. I thought Porsche supplied parts dating back to their earliest models. My mechanic and I searched everywhere with no luck. Two dealers said I can order it from Germany but it could take up to 6 months!!!