OK, So I have read the past threads with the BPV being directly involved with P1688. I have the same prob as past thread started by Mikey52 on 04/25/2011 titled "P1688 code, how to check bypass valve?".

The only difference is my BPV loses vaccum (stuck closed) when it starts "so called" limp mode. With the car in limp mode, I try to move the arm in/out and it will move but will not hold vaccum until I shut down and restart.

So I finally tore my MINI (2005 MCS 100k) down and removed the BPV. Is there any signs to tell its not working right when removed from the intake. I tested the actuator by disconnecting and holding the hose end. It holds which means there is no holes or cracks on the diaphragm in the actuator.
...am I over analysing the whole thing?!?!

Should I just fork out the 125 bucks for the Detroit Tuned BVP and call it that and keep my fingers crossed that it was the problem. I hate shootgun troublshooting.