'90 pathfinder ugrades

[c_habet_7]

i live out of the country. i own a '90 pathfinder. my parents were the only owners. anywayz. i was gonna get a 240sx but with duty and **** i held off. i wanna pimp my pathfinder so to speak. the engine sounds like **** and gives like 14mpg which sucks. suspension and steering have already been taken care of. does anyone know of any popular mods i can make to the engine so it runs better and possibly faster and to the interior and how i can go about purchasing everything and installing. where to find these parts would be a help too. i realize that the engine has a lot of potential but i'm not well versed in the naturally aspired vg30de's potential so plz clue me in. thanks