I do not believe a flame arrestor has much if any filtering capability, other than stopping very large items from entering the intake system. On the other hand the K&N units are a true filter, plus a USCG approved flame arrestor, seems like a simple choice to me.
I raced NHRA Super Gas/Comp for 15 years and had K&N filters on all my motors, never hindered performance, and internals never showed any abnormal wear from grit on freshen ups.
Have a factory supplied K&N on my Mercury Racing HP500EFI, and will also have K&N's on the 565 going in my Cole.
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