it was actually not much. just a few trips to the junkyard and 5 bucks here and there.
i first got a intake from a 5.0 explorer. its bigger and air flows better helped even with acceleration.
2 inch taller tires i also got only bad thing is speedometer reads 3-5mph less than what im actually doing lol
then i read about an IAT (Intake Air Temperature) sensor that a 5.6k ohm resistor chip is placed and tells the computer colder air is going in and readjusts fuel mixture. i got the resistor off an old threadmill but most electrical things around have em. not a big difference on mpg but helps a bit. dont go with a 10k resistor because then pinging starts unless you use higher octane fuel.
MAF mod is an easy mod as well. youtube has the video on how to do it just type in MAF Mod. but all it is is just a trip to autoparts to get lik a 3 dollar socket to take off the black box off carefully and after thats done then cut the center divider then with sandpaper just smooth out rough edges on it and put back the box then install it again.
air doesnt like turning so doing that lets air flow better and MAF reads better and also adjusts fuel mixture.
what i did with mine was i got a MAF off an f150 since they are bigger and just swaped in the black box to the f150s after the divider was cut then back in the ranger it was big difference on performance too.
electric cooling fan to reduce drag.
e3 sparkplugs- burn more fuel that goes in than the old ones so fuel doesnt go to waste out the exhaust pipe
this website will let you know pretty much everything there is to it just gotta read alot but its worth it
http://rogueperformance.com/WelcometoFredland.html
go on it and it tells you how to do everything and how it works