Ericginpa

+1 on the maf sensor. A cold air intake soaked in oil can thow all kinds of codes. Under hard acceleration the engine is pulling in a on of air and often times oil from cai as well. That oil will gob up your maf/map sensors. If that's the case you usually can clean the sensor and be good to go

Macster

The repair cost may not be too great if the problem is just sensor. There are I'm sure -- based on the info I have for other models -- tests/checks a tech with the PIWIS2 diagnostics computer (and maybe a volt/ohm meter) can do that can pinpoint the cause of the behavior, if it is a sensor or perhaps something deeper, like a VarioCam solenoid/actuator.

If it is the latter two items the repair can run into several thousand dollars. (MY 02 Boxster had its passenger side VarioCam solenoid/actuator replaced some months ago and the cost came to around $3K. The 996 IIRC has an easier to get out solenoid which may (May?) help keep the cost down.)

This problem won't get better on its own so you want to get it professionally diagnosed and fixed.

Sincerely,

Macster.