Which such a small plenum the air will want to go directly into the #1 cylinder, therefore making the ITB's virtually useless. When using a wider/larger plenum and putting the inlet closer to the middle of the runners, it makes for a substantial increase in air flow throughout all 4 cylinders, rather than having it all cram into 1 cylinder. Plus, with the larger plenum and placement of the inlet it makes the flow fairly even in the cyliders making it not such a complete bitch when it comes time to tune. I can go on and on, but I hope that sums it up for you. It's all about flow.