The following mods have been mentioned as being free / cheap (under $50). Please feel free to suggest more. Note: Changing seats at $50 p/ seat does not equate to a cheap mod - so do not suggest a mod like that.
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Aesthetic
Antenna - non-powered to powered, chrome base to black & vice-versa
Brake light - overlay/cutout
Bumper, front - remove plate & fill holes
Bumper, rear - sag fix
Calipers - paint
Center console - 98+ to pre-98
Clear corners
Debadge
DETAIL! - wash, wax, vaccum, etc.
Daytime Running Lights - install
Door sill plates
Emblem overlays
Engine bay - colored couplers & tubing, engine braid kits
Eyelids
Fog lights - "fog light mod", change bulbs
Grilles & oval - change, paint
Headlights - change bulbs, eyebrows, paint/"Hightower"
Interior - paint trim pieces
Knauberize
LED changes
Mirror bases - paint
Pedal covers
Rear valance - paint
Sail panels - 98+ or pre-98
Shift knob
Sidemarkers
Steering wheel - Ford logo from Focus
Stickers/decals - PM CEGer parkedcar
Taillights / rear reflector - paint, tint
Trunklid - swap w/ someone who does/does not have wing/spoiler
Wheels - chrome valve stems & caps
Duratec Maintenance
A lot of maintenance is inexpensive - plugs, wires, etc.
MAF - clean
Oil separator / catch can - create & install
Run Berryman's / Seafoam
Throttle body - clean
Throttle hang fix
Duratec Performance
Exhaust - SVT for non-SVTs
Heatshield - make
Intake - K&N drop-in
Intake snorkel - remove
Pre-cats - gut
Throttle body - optimize
Y-pipe - optimize
General Mods
Clock - install for those that do not have one
Cupholders - revised
Hood struts
Hoodliner - remove
Shifter - cut, remove reverse lockout
Steering wheel - cover
Suspension
Bushings / inserts
