This is my view on k&n they do let a better air flow when new , but with age and cleaning the filters can be over Oiled ( maf ) but most owners don't change them regularly enough and the Material breaks down causing dust Particles to enter the system . On the p38 you have two choices on blanking a blank off kit or block it with the penny no one has made a DIY blank off for the l332 like the penny on the p38 so what's wrong with the kit
not a waste if it stops the egr getting gummed up and causing a nuisance .
As for the exhausts go for it I'm going to get ss replacements when mine fall off .
As least your looking after it nothing wrong with being proud of what you have !!
Enjoy.