I have an OBD made by Autel....bought few yrs ago. Sealey are UK distributors for Autel now. Mine allows choice of manufacturer, fault diagnosis and clearing, live monitoring of the engine( during a run) etc.unfortunately mine is no longer supported for software upgrades but not an issue yet. It does my 2002 Plus8 ok. If replacing then I would be tempted by the Torque smartphone app with a plug in Bluetooth adaptor as it gets decent reviews and is cheapish.
