Hello, I have a 2008 r55 with 120000 miles , when I get into higher elevations 2000 and and up , my car goes into limp mode with little or no boost. No codes just half engine light on Speedo, so far I have changed out the diverter valve and intercooler both stock , and checked all my hose for cracks ect , any other ideas before I throw more parts at it
thank you

 

Get a code reader and see what cods it spits.