Free" in all categories, except Stock

• Changes within model range, including engines and transmissions
• Modified ignition
• Removal of air cleaner
• Modified carburetors
• Electric fuel pump
• Wet sump modifications
• Modified oil cooler/filter
• Substituted roller bearing cranks
• Balanced/blueprinted engine parts
• Chain Tensions/Guards
• Exhaust modifications after the header (car must still comply to emissions and noise restrictions)
• DME EPROM chips (except where effect turbo boost)
• Limited suspension adjustments (must stay within factory range of adjustment; no machining allowed)
• Removal of hydropneumatic suspension
• Substitution of coil springs/torsion bars
• Substitution of shocks
• Substitution of sway bars
• Rear camber compensation
• Suspension bushings
• Springplates
• Offset rims, tires, spacers
• Substitution of brake parts within model range
• Drilled rotors
• Brake pads, linings, lines
• Limited fender modifications
• Reduced tire circumference (within limits)
• Wheel diameters (within limits)
• Retail gasoline/additives
• Spoilers
• Limited interior modifications
• Roll bars
• Gear shift linkages
• Seam reinforcement on 914 model
• Spare tire

"Handicapped" in all categories, except Stock

• Lightened flywheel
• Modified venturies
• Modified velocity stacks
• Overbore up to 1.2 millimeters
• Machined suspension modifications
• Front shock tower brace
• Reduced tire circumference (outside of "free" limits)
• Limited slip differential (even if factory installed)

Not allowed in Stock, Prepared; handicapped in Improved; "free" in Modified

• Increased compression ratio
• Fuel system modifications
• Displacement increase
• Small diameter wheels
• Non-standard gears
• Modified fenders and wheel openings

Not allowed in Stock, Prepared or Improved; "free" in Modified

• Modifications outside of model range (including engines and transmissions)
• Engine substitutions outside series (factory-built race cars only)
• Modifications not listed
• Superchargers
• Turbochargers (except stock)

Not allowed in any category except Other

• Non-Porsche engines

Not allowed in any category including Other

• Nitrogen bearing fuel