DME relay is located in the fusebox under the bonnet (scuttle panel area NS) yes very common thing to fail, usually with heat iirc
good idea to carry a spare, cost £20-25
can be bought here -
http://www.porscheshop.co.uk/acatalog/p ... a13_212496you can get them cheaper, non genuine but the ones above are genuine
As for the catalytic converter, 89, im pretty sure its got one fitted, might be on the options sticker if its not always fitted "157" i think 0xygen sensor and catalyst but if its standard fit then it wont be on there
i know my J plate S2 did have one