I have a 2002 B4 and love the whole driving feeling of this car. I have other Subies and the B4 is my favourite long drives car. Mine is the auto version and I don't really get this 'valley of death' feel. I don't have a knocking sound and you may want to have that checked before looking into getting any tunes done on your car, as this could get worse. Do you use 98RON or above fuels in the car? Has the car had any major services recently? As for gaining extra HP, then you really need to upgrade a few items before getting a tune. I would join RSLC (if you haven't already) and get some advice from off there.