Discovery TD-5 Turbo Problem / Low RPM Flat Spot

[neutral 3]

Hi all, as above, late 2003 Discovery, when pulling away, the car seems to hit a flat spot @ circa 1,500 - 2,000 rpm and struggles to build revs. It doesn’t happen all of the time. Could it be the turbo actuator ?
The Landy has sat for over 4 months due to the steering box failing.
Driving it now, it’s performance seems really lethargic to how i remember it was, early this year.