I have been informed to leave the control unit alone unless you know of a good auto electrican, Im sure its possible to cut and splice the cables but belling the relevent ones out could prove awkward, the unit consists of a fare few resistors. I do have a unit spare and a good multi meter, I may have to have a look as to the routing of the circit and post my findings.
Most of the sensors around my engine have been by passed brakes, coolant level and windscreen washer , the cables only need to be joined together to stop the control unit led iluminating.
All the series 2 1.7s had hydraulic tappets , the 1.5 mechanical. Adie at Ahm built my 1.8 engine using a 16v block with 1.5 heads and big mechanical valves to allow the engine to rev alot higher.