Why does my 1997 spec. car lose power around 4-5000rpm, plus there I can hear a low resonance hum?
A. There seems to be a recognised problem with the 1997 specification cars blow off valve. This does not shut properly under boost and thus vibrates giving the sound similar to someone blowing across the top of an open bottle. I have also heard that it can also sound like a steam train whistle in extreme circumstances! When this problem first occurred the faulty valve was replaced with an item identical to the one taken off. No surprises when it failed again! Subaru have now introduced a new improved blow off valve and I have not heard of the problem occurring lately. Meanwhile the 1998 model seems to have a totally revamped and larger blow off system, but I have had reports that the problem sometimes still occurs on the early cars.
