Hello my name is Dave.
One of the most common causes of this issue is deteriorated vacuum lines going to the boost controller, however it would be greatly helpful if you could give us any trouble codes that have been stored in the PCM, if you don't have a code reader or scanner most auto parts stores will read these codes for free. If it is the vacuum lines going to the controller are bad it should be reasonably obvious through a visual inspection, the other common cause is a bad boost control solenoid. Your car has 2 solenoids and if you can find a code showing one to be faulty you can switch their positions and see if the code remains for the same position. I have attached a diagram showing the solenoids and vacuum line routing to assist you in tracking down the issue. If you aren't able to track it down with this information and you could give us the trouble codes we will be glad to help you further. I hope this helps and thank you for using 2CarPros.
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Thursday, October 31st, 2019 AT 8:56 AM