I might suspect Aftermarket Supplier if it didn't say OEM. Let me know what you find. You're a bit of a night owl aren't you? Almost 1am there!
I think your on the right track. The reply back said "The only difference is who we buy the part from on 996-106-011-56-OEM ". No explanation on the 97 and 98 model year only part, so I replied back asking again why they are for 97 and 98 model years only.
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2003 Boxster S
| 987 Air Box | K&N Air Filter | 76mm Intake Pipe| 996 76mm TB | 997 Distribution T | Secondary Cat Delete Pipes | Borla Muffler | NHP 200 Cell Exhaust Headers |
So if I'm reading this correctly, according to Pelican site, Pierburg must be OES, OEM and AS, but only for 97 to 98. Later years may have different manufacturer?