Air filters

IIRC, one of the car magazine back in the day did an experiment and found that running a base plate that eased the transition of air into the throat of the carburetor provided better air flow than running nothing.

If you are really serious in maximum air flow and can find room for it, a particle separator is superior to a filter. Properly sized, they can handle a 1100 shp turbine. Since there is no media, cleaning them involves emptying the trap.

It would be misleading for me to say that there is no restriction using a particle separator. Most of the restriction is used to generate the cyclonic forces necessary to throw contaminants out of the air stream.