1. The air intake system up to, but not including, the engine inlet may be modified or replaced.

A. The engine inlet is the throttle body, carburetor, compressor inlet, or intake manifold, whichever comes first relative to the intake flow.

B. The existing structure of the car may not be modified for the passage of ducting from the air cleaner to the engine inlet. Holes may be drilled for mounting.

C. Emissions or engine management components in the air intake system, such as a PCV valve or mass airflow sensor, may not be removed, modified, or replaced, and must retain their original function along the flow path.