your 100% correct, it is a APC, and it does rob the power on the top end.
i’m still waiting on a 4" cobra elbow. i’ve tried everything else. The only filter i havent tried yet is a HKS mushroom filter. But as it sits, the APC filter actually pushes my radiator into the core support. So the filter is wedge’d in there. I pull the rad when i need to remove the filter. If the cobra elbow works, i’ll put a big K&N on it.