any idea what the boost should be? could either be a split betwen the turbo/actuator in the pipe that runs between the two. this would explain the boost spike from the normal 8psi to 14psi as it fools the actuator. thats assuming the car should boost at 8psi.

if the car is set at 14psi but is dropping to 8psi id be looking at boost hoses for splits. the backfiring though i cant explain, i know nothing about efi. cou;d it be lean/boost cut or intermittent fault with the ecu.

definitly a fuel related issue? surge in the tank when less than half full can cause similar issues when using poor quality pattern tanks or the incorrec tank