2002 Altima fuel pump

I have a 2002 nissan altima 2.5 4 cyclinder. My wife was driving the car when it started to sputter and miss. The car would not go over 20 m.P.H. The check engine light is not on. The car will start and idle just fine. Wnem you rev the engine up it does fine until it reaches 2000 r.P.M. And it will spit and sputter like it is starving for air. I was told that it could either be the fuel pump or the mass air sensor. Also does the fuel tank have to br dropped to access the pump or can it be reached through a trunk panel. Thanks!