Hello to everybody,
I'm italian and I write you from Italy...first of all I'm sorry if my english will be not so good...I'll try to do my best.

I have a lancer evolution 9 gsr with big bore tb and complete exhaust system from elbow to back.
Now I find a problem with the boost...

When I put 100% throttle the pressure goes to 1.7 of peak and after jump immidiatly to 1.0 bar to rpm
end...

I change wastegate actuator with a new one...change also the actuator solenoid valve and check every hoses...also check bov and everything is working fine.

When pressure start to loose I heard a sound like a vavle that open and pressure goes out from there...

Can you help me to solve this problem?

Many thanks

 

Boost leak, bad. Check your lower intercooler pipe coupler.

 

Also do a boost leak test.