Modification	What It Does	Result	Possible/Necessary Changes
Air Filter/Intake (Turbo?)	Could increase air flow (leaner fuel mixture) to the intake	Can increase (HP) performance, also could (slightly) increase combustion chamber temperatures.	Use of a colder (heat range) plug could benefit engine performance if an air filter is is used with other modifications (not necessary).
Exhaust Pipes Headers	Improves volumetric efficiency (engine breaths better).	Can improve (HP) performance (by lessening exhaust restriction).	No plug changes required (exhaust modifications do not influence combustion chamber characteristics).
Performance Chips	Leaner fuel mixture. Advance ignition timing.	Can increase (HP) performance, also could increase combustion chamber temperatures.	Use of a cooler thermostat and/or colder (heat range) plugs could benefit engine performance.
Liquid Propane Gas, LPG	Burns cleaner. higher octane level.	Higher combustion temperatures.	The ignition properties of engine powered by LPG may experience greater spark durability and better performance by decreasing the gap by 25% and using a colder (heat range) plug.
Ignition Systems	Can provide an increased current flow (when plug gap is increased, no more than 8 mm) and better spark conductivity.	Crisper (more amps) spark, improved combustion efficiency.	May need to use an extended gap plug, no heat range changes are necessarily recommended
Cams, Valves, Timing, Duration	Improves volumetric efficiency (breathability), allows greater air/fuel mixture volume into the combustion chamber and improves exhaust gas release from the chamber.	Increases (HP) performance.	May need alternate heat range plug.
Compression Ratio (Increased)	Creates higher combustion chamber temperatures.	Increases (HP) performance.	May need alternate heat range plug.