98triplebackdroptop

I recently bought a 98 trans am conv its my first one so im new to the ls1 scene. I was driving home today and the engine light came on the codes are p0151 and p0131 the car idles fine and runs fine no hesitation pulls hard but seems to be going thru gas like crazy I'm not sure if I should replace both of the o2s before the cat or could something else be causing this? Please help!!! Also ive noticed the temp gauge stays at 180 never goes any higher??