I'm getting some hesitation with my 96 blazer and i'm pretty sure its my fuel pump. When i went under my vehicle to take the cover off my gas tank i notice that under the rear bumper gaurd there is a sqaure box about 10" by 10" with the fuel lines from the gas tank going into it. What exactly is this box and what does it do and is there anything in there that can be causing my problems? I changed a fuel pump in my 97 blazer last year and i did not see anything like this in that blazer. The only differance between the two is one is a four door and this one is a 2 door. Thanks to anyone that can help me with this.