Ummm, I don't know about you, but I wouldn't replace a fuel pump on the side of the road. It includes taking out the rear seat.
... secondly, most likely what happened was you were not tuned for these mods. Driving caused the engine to "explode". You most likely have major internal damage. Hence, the marble sound.
... and thirdly... 2005 WRX STI wagon? Is it an EJ20 that has an STI turbo? Any upgraded turbo better be tuned for.