I just bought a walbro external fuel pump. i bought it off some guy who had it on his sr20det 240sx. I am not sure how to install it, or even if I bought the right thing. Should I have got an internal???? This was sold as a ZEX 275 l/h fuel pump, but it is just a walbro GSL392 pump. lemme know if i f*cked up and just wasted $100 thanks