Got a mate who has my99 Classic (facelift) impreza wagon, standard spec, who has recently noticed a problem when accelerating through the rev range - found a flat spot during boost which then corrects itself later on,
I know my own td04 turbo runs out of puff not long after this until the next gear change, I'll try to get more information about exact symptoms, any ideas please boys?!

 

need to check the usuals mate. coils, plugs, maf etc