2001 a6 avant 2.8L won't start
 

I have a A6 avant with the 2.8L and it won't start. I thought it might be the fuel...got fuel and spark. I pulled the fuel pump fuse cause it acted like it was flooded... starts but stalls when it runs out of the available fuel and when I insert the fuse, it won't start. Changed the fuel press regulator, no difference. Only code showing is from me cranking on it. Cleaned and gapped the plugs. Checked fuel pressure, good. Checked MAF, good.......could it be plugged catalytic converters?......any Ideas?