i would say such filters are beneficial,
But there is also a foam performance filter avalible specifically for the P6 V8 from 'Uniflow'. They are an Austrialian firm and have them listed on there website. I cant remember the part no. off hand, but they come as a pair to fit in the airbox and are v.cheap.
Its worth getting the 'oil' for the filters at the same time (called 'Unifix' I think), but they come oiled, ready to fit. When they become dirty you just clean them in turps, dry and re-oil, like K&N's!
Got them on both my V8's, brill!