darkfiregt

Anytime you change something in the airflow, you need a good tune to compensate. If you leave the insert in, you really won't see much of a change because your MAF size is unchanged. There is a bit more airflow, but without the computer being updated, the car doesn't know how to compensate and that's why you're seeing worse performance. If you remove the insert, you must have a tune, as you are changing the size of the MAF. With a good tune, you'd see a big increase in performance, throttle response, and fuel efficiency.