Room for improovment!

[Turbo Haraune2]

Just lifted off the intake manifold on my EJ20 today and found out that subaru have cut som corners in producing the intake.

The openings in the intake dont line up with the intakeports on the head.
Misalignment up to 3mm at some places.
I guess this is because the intake is not machined after casting.
Also need smoothning of cast seams inside intake manifold.
Easy to fix if you have a airdriven handheld rotating file or similar(dremel). Just use the gaskets as a template and file away the extra material obstructing airflow. You gain atleast 5hp.

Call it a match porting job.

[Eatoniashoprat]

What people also do is port the throttle body edge to a blade and if your motor has them remove the tumble generator valves also known as 'tgv delete' on subaru forums.

Good call though, that is definitely some easy extra hp's! The subaru tuners from my (limited) experience go crazy about these details about making the intake tract as absolutely smooth as possible. Even bypassing the throttle body/idle air solenoid coolant lines in case it heats the intake air a small amount. Its also an easy mod, you don't really even need any extra hoses.

Mike