hi phil im new to this site i also have a b4 from japan,purple with smoked gold subaru alloys,and hated that lag between 3300 and 4500,im a fabricator and have done loads of exhausts before so i whipped the standard exhaust from uder the car,(the start of where the exhaust goes 2 into 1 under the car up front),thers a cat and a silence in the straight section and then the backbox,its 60mm tube so i replaced the entire length with slightly bigger 75m(3inch)stainless,first thing it SOUNDS AMAZING!!!!! what a growl form the boxer engine you can really hear whats going on,and i instantly noticed the power gain the flow gain was so good the it now pulls strong through the old lag point 3300 -4500 ish,would reccomend to do this 110% glad to help(i hope to take the second cat from the downpipe<its in the left side downpipe from the turbo its two into one)