Legacy RS

If anyone else here has experienced problems with the knock sensor being triggered by stuff like a ticky/tappety head thereby stealing loads of power from your pride and joy, please can you give advice on ways around this.

One of the heads on my car generally taps constantly a tiny bit which seems to make the knock sensor think there's detonation going on so the ignition gets retarded loads and it loses tons of power. I know this is a notorious problem from reading about it on other forums but wondered what sort of fixes people may have tried to solve this. Insulating the sensor slightly seems to be a popular choice so they only hear proper knock and not gentle ticking but what's a good material to use?

Also I know this is a bad problem on Legacies but are Imprezas affected to the same extent?

Thanks for your help in advance!
Jim