Clean your MAF before you replace it... this may make the ECU read the system fine and it will then say your cats are A-OK. The cat readings are based on before and after results from the O2 sensors, which work in concert with the MAF.
Some of the forum guys have had great luck with cleaning the MAF (do a thread search to find out what they used to clean it and how they did it).
Just in case you don't know about Sunset Porsche in Oregon, they sell Pcar parts at wholesale plus 10% plus shipping and no tax. MUCH cheaper than your stealership's parts counter, I assure you.
I had to sink about 3k into my old boxster the first year I owned it. Then I drove it from Houston to Northern California and back, and took many other long-distance trips without one single problem.
Fix it up a little, and this car will give you far more smiles than you spend in dollars, I assure you
