Hey thanks for the input. I am glad you are happy with the intake.
I think that there may be an option in the future to constrict that area of the intake. But for now, I don't forsee that since I don't want to have to sacrifice airflow performance. In my experience, installing about a dozen of them, I didn't have to cut the duct cover. I had said earlier that there may be automotive tolerances that effect it, although am not 100% certain if the tolerances are off by that much from car to car (I would guess to say you are right and they aren't off by that much).
The cover that touches the big mouth will be
close to flush but definitely not all the way flush, (I am sure you did it right from what I read). You don't absolutely have to cut the cover if you dont want to. The cover will still go back on and the clips should still pop back in.
There will be touching between the stock duct cover and the intake, there is just no way around that since the intake is much larger than the stock duct hole, it lets the engine breath and it is a bigger opening than stock.
Just for reference I wanted to shed some light on the design.
The stock duct cover is a tiny opening, you can barely fit an open hand through it if you reach under there. The engine has to breath through this puny hole. When I designed the big mouth, I had to balance performance, aesthetics, manufacturing and tolerances. Since the FiST guys wanted performance (there are very few options for true performance intakes out now for this car); I focused on getting the duct to be aerodynamically most efficient while doing the best I could do fit it inside that tiny stock hole. If you want to cut the cover, you certainly can, but I don't feel that it should be cut (tomato tomatoe!). You can put the stock plugs back in their respective locations. Again, sorry for any inconvenience or if the instructions were not as clear as they need to be, I can revise them how you feel they need to be revised. Just let me know.
Here is a quick image of the stock duct cover on a 2016 I installed last week. There is a slight gap, but at least for me, the extra airflow, totally worth it.
Best,
D