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There are four problems as I see it:
1) The actual compressor itself is designed to be mounted straight up and down (it has a rectangular cross section). In actuality, it doesn't fit in the car that way and must be installed at an angle. Because of this, there are questions as to whether a steady supply of cool oil can be supplied to the bearings.
2) The Boxster's engine already has a fairly high compression ration of 11 : 1. Forced induction on an engine with this much cylinder pressure adds tremendous stress to the internals; these stresses will far exceed the design parameters of the structure and material used for these parts. Generally, any normally aspirated HIGH compression ratio engine that is going to be force fed properly will need to be modified to lower the cylinder pressures by lowering the compression ratio with custom pistons and by profiling the camshafts for a safer duration / lift. The TPC supercharger attempts to ignore these constraints by simply lowering the overall pressure output of the compressor (VERY modest boost).
3) The system is obscenely expensive: $4700 + 2 to 3K installation for a modest power gain, shortened engine life, questionable reliability, overstressed internals and NO modifications to the stock engine to compensate any of this (not to mention the STRONG possibility of leaning out your motor under boost and overheating your components). That is a ridiculous amount of money for a bolt-on kit of any sort, especially a bolt on kit for an already highly stressed high performance and LIGHT motor.
4) Since you want to do this to your car, it won't be too long after you install the TPC that you decide to swap pulleys on the supercharger for a bit more boost. When you do this (and you WILL be tempted), engine failure becomes a virtual certainty. All it takes is punching the throttle before the engine is warm and sending a nice, dense, cool blast of air into a supercharger to be further compressed and then ignited, turning your beloved pistons into swiss cheese.
5) It's roughly $7K for the supercharger / install. It's roughly $10K for a 996 engine / install. That yields at LEAST (depending on what you do to it) 300HP of normally aspirated power from an engine performing WELL within its design limits that all dealers know how to work on. The supercharger is a cute idea. Maybe a great idea for a chevy or something with a carburator and an 8:1 compression ratio, but a 'bolt on' design for an 11:1 compression ratio in a late model Porsche is a disaster waiting to happen (although it will be fun for awhile). These are the exact reasons that there is no viable turbo kit for this car that does not require engine tear-down first to beef up the components and lower the compression ratio.
If you want info from a shop who's done a TPC supercharger and five 996 conversions, call Cars II / Racer's Image in Melbourne / Palm Bay, Florida. Have fun. (Hint: The supercharged car met an untimely demise and was swapped for a 996 motor. The Boxster's trashed motor sits on their shop floor to this day).
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