Steppler

Ok guys here's the problem. I seem to be suffering bad fluctuating boost. Car is MY02PPP 33,000 miles. Noticed during summer slight fluctuation but seems worse now colder weather is here. Car will boost up to 1.4bar then drop to 1.1 -1.2 then generally hunts around. Done the usual, cleaned boost solenoid/pipe work but still no joy. Anyone got any ideas

Cheers

Mark