Hi guys

My 1999 Subaru WRX is having some acceleration issues. At about 2600 rpms the car bucks and lacks acceleration. I've also noticed I can't hear the 'winding' of my turbo. It doesn't appear to be kicking in. Can anybody shed some much needed light? I mean if it is a turbo issue and if I'm looking at a reco turbo job, how much will this cost to do?