Help needed for emision problems

Hi to all,
I am having major problems trying to get my 1994 LSE (lpg converted) through the mot, the garage I use cant find out what the problem is. When they put it on the emision test the HC is well over 2000, they said this is un burnt fuel. Does anyone have any idea on what could be wrong as I desperatly need to get the car sorted out.

Any help would be much appreciated

Welcome to the forum,your RR is pushing lots of unburnt fuel out - this much should have a fairly obvious cause - running on Lpg and petrol together would do it,as would a misfiring spark plug.With this kind of Hc reading looking at oxygen sensor readings is a waste of time,try clamping off the gas feed pipe to the "cooker ring" - inlet for the Lpg.This way you can be sure the engine is running on just petrol.You need to get it to run correctley on petrol before you even think of gas - including passing a Cat type emission test.Check all the ignition system components,plugs,leads,cap and rotor etc.Cap and rotor need to be genuine or Lucas to be any use,all the ignition components must be 100% to work with gas.
Does the car drive properly,if there are any poor running issues what is the history to them ?