Hi Alex... your not gonna believe this but I too had exactly the same problems after I had the conversion. The LPG fitter was at his wits ends trying to fix the problem. Before I tell you what the final outcome was let me let me tell you what I did. I joined the AA extra repair. That gave me upto £2000 of repairs a year for only an extra £50 on top of the normal relay/roadside repair. Now let me tell you what happened after that. I got a mechanic who just happened to be a friend of the LPG fitter and got him to have a look at it. This guy who I shall name Tony used to work for the AA. Because my management light came on I called the AA and they could not fix it at side of road but followed me to Tony's garage...following me so far? Tony, who just happened to work for AA a few years ago diagnosed the problem as coils which is fitted to each cylinder. It turned out 3 had gone. He replaced each one and sent AA the total bill who paid it and hey presto... the old beast is working fine again. My advice???? Get a diagnostic check, if it turns out to be your coils also, join the AA. Dont tell em I told you. Let me know how you get on. Steve B