I'm using the single K & N type of filters on my 8 stack. Some of the screen type can be too fine and rob HP and others are too open and can suck in debris.
On "Motortrend TV" channel on youtube had a 613 HP Hemi and on the dyno the screen brought it down to something like 460 HP. If I can find the vid I'll post it.
With the K & N oval type I had, I put a fair amount of the spray
oil , and it choked the TQ & HP by 20 & 25. Lesson, spray them lightly !