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i think maf location with respect to blower, and whether there is a blow-off valve, will affect whether a tune is needed. if the blower is after the maf and there is no bov then it is a closed system and the computer sees all the air going to the engine. if the maf is after the blower, then the air is pressurised at the maf and the maf will not provide a proper reading (it measures flow, not pressure, so more air will be getting to the engine than the computer knows, resulting in higher combustion temps and holes in pistons). or, if there is a bov after the maf then readings tend to be inaccurate as air will be leaving the system that the computer doesn't realise.
most aftermarket turbo applications i've seen for the boxster have the maf before the turbo, while most s/c kits have the maf after the blower. uncertain why, perhaps to address reverse flow past the maf in s/c idle conditions.
another issue is how your kit approaches fuel. some systems work with the existing computer/injectors, while others use a piggy-back computer with a 7th injector. more room for error in the second application.
some research on Imagine Auto might be in order; from what i saw, their kits were not on the market very long ...
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