System too lean, Right and left

This is what came from the OBDII computer at auto zone. The codes where P0171 and P0174 on my 2000 camaro. I think it might be the O2 sensor but im not sure. The service engine soon light would come on about 40 min into my drive between Phx and Tucson doing 75-90. Then it turned off when i would do some city driving. Has been off for about 3 or 4 weeks now after that drive.
Any suggestions???
thx.

check your fuel pressure