Originally Posted by skinless
there is a very slight power lag when acelerating.
Which does seem to fit the symptoms of which you speak.
It is possible that the leak is on the low pressure side (ie. between air filter and turbo) although it's more likely that this would manifest as an audible whistle.
In my opinion this could be easily fixed with a quick visit to a Ford dealer - the 2.0 engine is well known to them due to it's common (and very worthy) application in the Mondeo 2.0 TDCi models.
Don't think of it as a Jag with a Ford engine, think of it more that some folks are very lucky to be driving Fords with Jaguar engines.
You better placed still, you have a Jaguar with a Jaguar engine.
All said though, do get it sorted, anything with forced induction (turbo and conventional superchargers) will suffer if there are air leaks anywhere.