Is it too much airflow? The airflow is still limited by the intake itself. The Kinetix or spacer just changes the size of the plenum. It's why they make different size spacers, the different heights change the characteristics. Typically the thicker spacers result in minimally more power, but on the top end at a cost of low end torque. So if you stacked a Kinetix on top of a spacer, you'd probably lose a ton of power because the powerband would be shifted so far right the engine would never rev that high and the intake tube can't move that much air. If you were boosted, there may be some benefit. But no one has ever done it because it wouldn't fit and at that point, you might as well get a real aftermarket plenum like a Cosworth or one of the crazy one off's I've seen on some Z's.