Perkins M30 air filter

[38mess]

My Perkins gennie has been running perfectly over the last five years, I recently took the injectors out and had to order a return fuel line, the guy on the phone persuaded me to buy air filter inserts which are just small squares of foam, he sent three.
When I took the air filter housing off it was empty... Do I fit the three or just one and keep the rest as spare? Three fit in perfectly. Or just leave it empty?

 

[westhinder]

My previous boat had a Perkins Perama M 30 of 1988 vintage. It had no filter element in the housing and did not seem to miss one. When I sold it, it was 22 years old, still running sweetly without filter.
I can imagine the same engine in a digger or a generator on a dusty farm would be less happy without one, but a boat is not a dusty environment.