Can't vouch for the K&N panel filter, but when I had my 2.5 V6, I fitted a K&N kit with heat shield etc... noticeably changed the sound of the engine, even at idle, but wasn't obtrusive.... It may be subjective, as I could never prove it, but I did feel that acceleration was improved a little, and my fuel consumption didn't change that I noticed doing 300 miles per week.....
I picked my kit up used for about £40.... and would say it was a good investment for me..
Cheers
Phil
