I had an AC Stag fitted to my Omega elite 3ltr back in December last year! I have had no trouble whats so ever. The cost of filling up the 85ltr tank cost around £55 and that will do between 290-320 miles (mostly m/way) that being fitted by ProfessAutogas for £1100 sounds to me that some people are prepared to try and save themselves money by purchasing the kit and doing a DIY on the Omega, let the Experts fit the kit.
AC Stag only describes the ECU

The issues we've experienced are minor and most likely relate to tuning. Personally, I wouldn't pay a "Professional" to install any LPG kit to may car because I've not seen a job worthy of the money (except for Entwood's)

For £1100 I doubt they removed the manifold before drilling it... 90% of the time this will be fine but I'm not willing to take the chance of swarf damaging my engine

Equally... I fitted my kit myself a little over 2 years ago and, apart from the little hiccup as it changes gear at full chat, it's faultless. Yours could have exactly the same issue but be set to switch to petrol and hide it

At the end of the day, you do what you are happy with... I don't let many people work on my cars... Never have and am unlikely to at any time in the near future.
