I'm not sure about the supersprint but I know there are a number of manifolds out there offering some amusing BHP gains.. Madeno racing, AW-delta, Auto Delta & Barry Waterhouse seem to be the biggest names.. most offering around 20bhp increase.
Andreas or Juan may be the guys to ask on that one..
I'm at Buenos Aires where those 'famous' brands are not available, however I have installed one of the best exhaust we have in Argentina.
3" from the turbo straight onwards and a back box, all stainless steel. Difference is not amazing but really noticeable in the whole range from low down. I think I have gain of arond 15/20 bhp. Plus the enjoyable burble from the exhaust.