Well, as a small update, I cleaned out the ducts removing any residue, replaced the intercooler & also had a software update carried out on the ECU by local Saab dealer. Over the last 3 days there has been a tiny puff of blue from the exhaust which is far easier to live with than the cloud which previously engulfed the car. Incidently the cloud reduced after the software update which was carried out a few days before changing the intercooler.