The_Phantom

If you suspect that it's bad gas, you might want to try a bottle or two of gasline water remover. Usually a dollar or two a bottle at an auto parts store. (A similar thing happened to a friend of mine. Her car would stall and was difficult to start because of watered down gas and totally cured by the water remover.)

Gretch

I would be surprised if the car would idle at 200 rpm, that is prox 450 rpm below spec. A vaccum leak would cause a high idle, not a low one. Pinging (predetonation) is caused by either too lean a mixture, or too low an octane rating (for the engine operating conditions). Oil in the fuel (bad rings or valve seals) can cause oil in the cylinders which can be a cause for pre-detonation.

The combination of predet and low idle may be an ignition problem. Perhaps start your diagnosos by checking your wires to the coils and your plug wires.........

BrianPA

I seem to remember quite some time ago reading about problems Boxster owners were expiriencing with after market intakes where by the MAF (I *think* mass airflow sensor) would get fouled up with oil somehow and cause poor performance. Since the engines are somewhat the same this might be worth checking. Either way I think going back to the stock airbox and a visit to the dealer immediately would be your best bet. Whatever it is it can't be good for your car.

SYMA

Well dealer seems to think bad gas as well but that is just a verbal call at this point. Later this week they are getting it in and hooking her up to see what the read out says.
I will keep you all informed.