Hi fozzy15, may I offer a belated 'Welcome' to the exclusive CX-7 ownership experience!!
I have been enjoying the reduced running costs of my LPG conversion, but suffered slightly due to the very flimsy connections onto the Mazda engine ECU, which did produce a sudden misfire after covering about 1000 miles since the conversion. The conversion installer was able to fix the problem within a short time, but otherwise the job has been a great success and costs me around 12 pence a mile depending on how I drive!
The only real criticism I can find with the car is the dreadful fuel consumption when you start to make use of the amazing performance, with very low 20's (or worse!) being quite common! This is not a real problem when using the car on LPG, as the cost per mile is still on a par with that of a much slower and more noisy diesel equivelent, and the performance is still electrifying!
I recommend using an experienced LPG installer for the conversion, and highlight to them that the ECU connection needs to be handled with EXTREME CARE! This plug needs to be removed to connect the gas ECU wires for the sensors, so there is no alternative but to disturb it. As long as great care is taken not to damage the pins, there should be no reason to expect any future problems.
To those who have not experienced the CX-7, I can only suggest that you take one for a test drive, as it is a very confidence inspiring car, and the Autocar road test summary states that it is 'The most dynamic SUV this side of a Porsche Cayenne'! Admittedly it also states that it is 'Fast and thirsty' which I can vouch for, but I still manage around 300 miles between LPG top-ups....around £36 a go....so pretty cheap motoring really for what you get. I mentioned about the petrol injectors needing to have some petrol through them to cool them in extreme conditions, and that it runs only on petrol when starting and warming the engine, which means that you need to keep some petrol in the tank too, but I have used only around £40 worth in 2000 miles, which can't be sniffed at!