Porting of the plenum is basically a free mod that will free up a few horsepower. This modification will not add "dynamic" horsepower that will bury you in the seat springs.....but moreso it will improve the response of your throttle. First some theory. The airflow entering the plenum is forced to make hard right angle turns to enter into the runners. There are square block areas to the left and right of the runner passages that can have excess material reduced to improve airflow.
For some reason GM put restrictive "blocks" in front of the EGR passages and to the left and right of the throttle body openings. You can grind down the front blocks and you can radius the side areas for improved airflow.
By curving your grind (radiusing) you are able to grind away excess metal without cutting through.
Be extra careful and go slow when making your radius grinds.
Suggested Tools : You will need a dremel tool and the above bits: Drum Sanding Roll Tapered Metal Cutting Bit Drum Metal Cutting Bit Tapered Sanding Roll
Basically take your time and grind away the areas above. The sides must be radiused to prevent breaking the outer wall. Use caution here and go slowly. You can always take away more!
