I just got back from the racing line where a load of us had the RR day a few months ago.
I'm getting 3 psi base boost so we were expecting it to run rich and be leaking out somewhere.
we were surprised when we put it on the rollers and got a steady 15.2 AFR at 3500rpm / 3 psi, too lean not too rich.
There were no obvious leaks and all the pipes were secured properly, and no mad hissing noises of air escaping.
We traced the problem to the intercooler, as the entry pipe from the turbo was rock solid with pressure at 3500rpm, but the exit pipe was limp, you could still squeeze it easily. There was no sign of any air escaping from it though so it must be blocked inside somehow
Time to find me a new FMIC then go back, hopefully it wont be stupidly lean when it gets proper boost again.