Does the 04 have the PI motors,what kind of backyard mods can be done to these motors without buying parts??
yes. and if you want hp on a mod motor your gona have to pay for it. on a n/a car just add CAI, thotlebodie and plenum, underdrive pulleys, handheld tuner (recomend sniper) and gears.
X pipe, gears,upper intake plenum, 75mm throttle body, cold air intake, underdrive pullies, timing adjuster, and a short throw shifter all of these mods shouldnt cost you more than 200$ each and you can spend a saturday morning doing pretty easly but horse power isnt free this day and age