Ok, It sounds like the car is on the stock MAP still.
You should check the local forum here and find a Tuner in your area or use one of the Tuners here and get the car off the stock MAP.
You mention since the 100K tune up. The plugs get changed every 60K.
You still may have a coil pack issue too.
199,000 May 12 new ej257 short block, Aug 11 installed VF52 turbo, @20.8psi, 280whp, 300ftlbs. CHECK your oil, these cars use it.
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