the TSR manifold does give good gains, but
if you get the TSR manifold you will need to get vibratechnic engine mounts or else it will crack the manifold with it being made of stainless steal
also, you car will have a really tinny sound from the manifold those this can be dampened down with exhaust wrap, but this just makes the exhaust hotter further down which can lead to other implications
do Janspeed not do a mild steel manifold for golfs?