I have an 89 camaro 2.8Lim getting a code 44 "lean exaust" but im not sure if its a fuel problem or an exhaust problem. In very hot weather I've driven for a long time and have heard the fuel in the fuel tank boil. Which problem could this be, a oxygen sensor or the fuel pump? Note: The check engine light has never came out until now.

It could very well be a bad pump.

More often than not, the O2 will trip a 13 or 45.

Have you checked the fuel pressure?

I would be surprised if its O2 sensor. I'd say fuel pump, filter or requlator.
Good luck

how can i test the fuel pump whith it still in the tank? i read that i can apply battery voltage to the ground terminal "G". but i dont ubnderstand what it means by battery voltage. where do i get battery voltage. also, what are some signs that a fuel pump is malfunctioning?

What do the plugs look like? If they look lean then the pump, regulator, or filter is probably at fault. If they show rich, then the O2 sensor may be the cause.