Fair point. Is there a technique that I should know about?
I've spent hours trying to get them off without causing [too much] damage to the clips.
I was the last one to change this filter just 2 years ago, and it was a breeze.
Sorry, I meant PCV as in Purge Control Valve (EVAP solenoid), not Positive Crankcase Ventilation.
Anyway, it was a loose air filter breather hose in my case (i.e. 'Vacuum leak on engine').
Oh, and it was P1130 not P1131. Apologies.
I got a P1131 code suggesting a problem with the PCV (accompanied by high fuel consumption and lack of pokey-ness).
I sourced a used replacement PCV from Spain via eBay and installed it. It made no difference.
Eventually, I discovered that the air breather hose that goes from the air filter...