Boost off the gauge ...HHEELLPPP!!!

[pdapaul]

Hi all,
Just purchased an 88 gtt to do up but have an issue with the boost. In every gear but first when it comes on boost the needle flys off the gauge and there's what sounds like a massive backfire. I've checked the actuator and the arm moves quite freely. I would be grateful for any advice.

Cheers
Paul

[scratcher]

Does the actuator move when you wiggle it or on boost?
Do you have a bleed valve fitted or a split in the line from the manifold to the actuator? If not, it sounds like the actuator has given up.
You can test it with an old valve and pump over the front port.