So I believe I've found the culprit of my boost issues. One of the vacuum hoses on the boost control solenoid is split where it connects on to the BCS.
As a test I taped it up with some insulation tape (GOOD JOB) and it does seem better but obviously not a permanent fix, I'd at least user gaffer tape for that. The bit that has split is the slightly larger hose that fits over the vacuum hose and the outlet on the BCS. Is this a specific part or will any hose of same internal diameter do the job?
Left hose, directly opposite the metal inlet under the electric socket. This is the BCS on the inlet manifold.
I've read a number of posts about boost issues, some of which are very similar of mine. I have checked most other pipes (all available from above) from the intake right up to turbo and what I can then feel up to the top hat. I have had a feel of the hoses on the turbo solenoid too and these feel fine. Initially I was going to just replace the BCS, and probably will do when I look to refresh the hoses/intake system during the winter. But for now I'd prefer not to even have to get any tools out! I couldn't find any reference to these specific hose end bits.
For search purposes my symptoms are:
Seemly pulls fine in 1st and most of 2nd (guess this is down to amount of boost in those gears)
Gets to about 3K RPM in 3rd and boost disappears, can hear a gush of wind as if it's all being expelled from the system.
Similar in 4th and 5th, but slightly lower revs.
I would also guess that my MPG is worse, but this is unproven.
