Throttle Body Help

Anyone on here have experience modifying GM Throttle bodies? This throttle body is off a 3.5L inline 5. Just wondering why there is a 4mm ridge on the bottom but the top is smooth. Would it be a net positive or negative to remove it. The vehicle already has a 93 octane tune, exhaust and intake. There has also been ignition upgrades and catch can system to replace the factory PCV system.

Smoothing the transitions/ridges should be a positive move because the turbulence from the ridge will reduce airflow.

It's important care be taken to avoid removing material where the butterfly approaches the bore, as control of the airflow there is important for idle quality.

The ridge is there to give more resolution at lower throttle openings by acting as a choke point. Some of the larger GM throttle bodies are scalloped for about 20% of the initial travel from 0% so that only one side of the opening is flowing. This gives better driveability with a larger throttle, whilst not choking flow at higher mass flows.