I have a bbx turbo and synapse DV, as well as other mods. My target boost is 30 when on e85. For the past year it was working fine.

After doing a road trip where i hit 5500 feet elevation my peak boost is around 27 to 28 now when back at sea level. I have no other symptoms. Any ideas on what this could be? There were no changes to the car during this period.

P.S. I did a boost leak test and it passed with flying colors, also i noticed it is running rich right now at WOT. Maybe i just missed a minor leak?

 

If its a boost solenoid then up the duty cycle. If its an MBC the turn it up lol.

 

Running rich due to less boost, and the tuner not setting up the fuel table to add/subtract fuel with increased or decreased boost and load.

Lower boost could be a number of things: Boost leak, bad boost control solenoid or MBC, something happened to the wastegate actuator, something happened to the turbo, something happened to your boost gauge or its reference source or it sensor. Lots of things to check..

 

Update -

so looks like its the synapse DV. Did another boost leak test and the valve was leaking badly in pull mode. I switched it to push and it held boost alot better, probably needs new O rings. Will call synpase and see what they say.