Do you have Leo's book? I would get Larry's manifold (exhaust, for a turbo, check the classifieds, on the left). Might ask him about what he thinks you should do for that setup.
3.55 and the OD in a 2004R is kinda steep, be carefull as too steep a gear will kill economy just as horribly as too short a gear will (but at least the short gear would have a performance advantage
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