Was the check engine light flashing when the accelerator stopped working or it stopped accelerating? Perhaps the car was in limp mode. But yes, get your own ODBII reader. I got a $50 one on Amazon that is Bluetooth capable and then bought the 'Torque' app on my Android phone for $5 and can read my codes on my phone. It also gives me the ability to see all sorts of parameters like air temps, oil temps, voltage, etc. in real-time.
If the only code that comes back is a P0420 or P0430 (which should be the Catalytic converter codes), then you can modify your exhaust for $50 to get past those two codes. Here is my thread for my M56 where I did that:
howto-p0420-p0430-workaround-fix-m37-m5 ... 66-30.html
Note: I believe a fully clogged/bad cat can cause all sorts of performance/power issues. AZ, can you confirm my understanding is correct?