The plate that Stillen is referring to is an Air Guide that is present ONLY on the NISMO. It is pop-riveted to the top of the aluminum crash bar. We have installed a handful of kits with plates left in place, but it takes some adjustment and fitment. We only leave these plates if the customer is 100% dead set on leaving them on. Otherwise, simply drill out the pop rivets and you are done. It might add 5 minutes to the overall install time to do this.
Here is a picture of the OEM Nismo Aluminum Crash Bar. I think there are 3 ~ 4 pop rivets per plate securing it:
For comparison, here is a picture of stock NON-Nismo Front Aluminum Crash Bar:
