I have five codes P2237 P2196 P2271 P0030 P0171 and a P2237 pending code on a 2005 elantra.The car runs poorly, bad gas mileage, sluggish with the check engine light on.Are all O2 sensors bad or maybe the cats plugged up? Any ideas?

P2237 P2196 P2271 P0030 P0171

These are all O2 sensor trouble codes, except P0171 which is a fuel trim code,

You have a bad 02 sensor - up stream - Bank 1 Sensor 1.

Replace it, then road test. The engine computer has a 'default' fuel trim it uses when an O2 sensor fails so it can protect the catalytic converter. If this hasn't been going on too long, good chance simply replacing the O2 sensor will remedy your problem.