M20
UPGRADES
INTAKE
For most Stage 0.5-1.5 M20, an upgraded drop-in filter is usually perfectly fine and offers a similar power gain to a full intake system. The stock intake box handles about 200 WHp relatively well. The M30 intake box offers a 62% increase in filter surface diameter and handles over 300 WHp relatively well. You can upgrade to a full intake system if you wish. A popular option is the KAMotors intake.
EXHAUST
The best bolt-on upgrade for any M20 engine is the exhaust manifold. The stock unit is heavy and very poorly designed for a performance application. A popular option is the Shmeidmann longtube system (shipping to the USA can be expensive however).
A cat-back exhaust offers the least gains in comparison to intake and exhaust manifold. 57-76 mm (2.25-3 inch) diameters are ideal, though there is minimal difference beyond 65 mm (2.5 in) diameter at lower modification levels. Please consider the weight difference to power gain and decide what works best for you.
HEAD
CAMSHAFT
VALVETRAIN
BLOCK
PISTONS
CRANK/RODS
==FORCED INDUCTION