Its a well noted fact that 98 blocks are prone to "piston slap" and Subaru are well aware of it !! . Irrespective of ya car having FULL dealer history etc , if its out of warranty they wont touch it .A dealer in Yorks said its your problem mate and Subaru Uk seem less than keen to help .... Buyers beware . This is a shameful attitude from Subaru uk and their dealers . Good luck with ya scoobies boys you are on ya own out there .. anyone had a result with this prob? hmmmmmm

This seems to differ from dealer to dealer, I've seen a couple of posts today saying Subaru UK won't fix this fault, but I have also seen posts in the past were people have had this done.
May be its Subaru's "We don't need customers any more" attitude that seems to be about these days.

I would more positively suggest, that its a dealer thing, as they sometimes cant be bothered to process warranty claims, or in some cases, when the warranty has just run out, or very low mileage vehicle, Subaru Uk, often consider a goodwill gesture. So, if not getting any joy out of your local dealer, try another one, they may be more willing to your problem.

My my97 cat had the problem when I bought and they fixed it, did have extended warranty though. But know a few guys that have had it fixed not under warranty, apparently though its not covered by the extended warranty.