keyan mentioned it but people seem to be posting uppipe and header and are forgetting that you also need the twinscroll flange on the downpipe which gets expensive.
you either have one made by hayward and scott, militek or roger clark motorsports and shipped from the UK or have a flange welded on here in the states which in the end isn't much cheaper.
80 dollar flange
250 dollar downpipe
200 dollar labor (at least, i've been quoted 3hrs and more)
that turns out to be an expensive downpipe
i've seen pics of the UK pipes and the only one i would consider is the RCM unit. I don't like the welding I've seen on the other two pipes i mentioned.