Need help on which O2 Senors to purchase please

[steved0x]

They are the same except the cables are two different lengths, hence two part numbers. Search for "mike focke boxster" he has a website with all the part numbers and he explains it better than I can. Yours may be different though since you have 2003, I think they may have changed.

You need 1 before and 1 after catalyst if you want to change them both.