Lo Gas instalation - help needed!

[smoker]

Hi, I have a "lo - gas" control system fitted to my Rover SD1 . There is a lambda sensor fitted in the exhaust downpipe.
The problem is the system doesnt seem to be working.When I bought the car the engine would only idle on gas. I found that removing the stepper motor plunger on the gas control valve allowed the engine to run but now i have no mixture control.
If anyone has any experience of he lo gas system I would appreciate your thoughts!