2004 9-3 2.0t limp mode after hard acceleration
 

I just bought an 04 9-3 2.0t the the previous owner was told that it goes into limp mode after awhile most likely due to a clogged cat. I got it home and I'm pretty sure it ain't a clogged cat. I got it to throw a code, (failed to write it down but it was something like a ECM), by redlining it threw 1st and 2nd gear. Then I cleared the code and it runs fine again. As long as you don't drive it hard the light stays off. But where's the fun in that. Anybody have anything like this happen to them? Or got a starting point?

Thanks in advance