I was told today that we had a landrover engine that had the same problem as your engine, it uses the same borsh unit as the Mk2 8v, that had a fault on it and made the car run lumpy with also a loss of power. No point buying a new one, get a second hand one off ebay or go to GWbridges in Crawly, you can google them if you don't know who they are. Will cost you around £40 quid.
Chris