Boost problem please help

[mike's r5]

Hi guys, having problems with my boost, the car was set up for 18psi in October after about 500miles I boosted it up at a set of lights and the actuator arm popped of the turbo which is when I parked it up for the winter, over the winter I changed the boost gauge and carb elbow and put actuator arm back on but now I only had 13psi which I thought was the new boost gauge, then recently about 2000miles later have only got 8psi so started to investigate.

I have checked intercooler pipes visually for splits and have tightened all jubilee clips
Changed the carb elbow back to standard
Tried a different boost gauge
Pumped actuator up to 20psi and held fine
None of this has fixed the problem

Is there anything else I can check.
Can someone tell me how to pressure test the intercooler and pipes
Any help much appreciated.

[Trevhib]

O-ring on the carb top?

Split in the boost hoses that only show up under pressure?

I can't remember how people have pressurised the boost circuit to check the hoses but a quick search should help. Otherwise you could fit someone else's hoses temporarily and give it a run out.