Air cleaner base

[Burke1118]

What’s the best air cleaner base and lid that provides the best flow? I see some different versions on the touring guys cars. Also while were at it.. what’s the best filter? I’m using a K&N 4” tall and seems to work well, but not sure if anyone on here has done any legitimate testing.

[Krooser]

R2c makes a nice flat base...others do too.

[Jim11h]

Paper my preference