Hi!

I bought my first range rover sport and I love it. But I have a problem, I get the codes p0171 and p0174. It runs lean on idle and its shaking abit. I had the car at land rover workshop and they couldn't find anything. The car is lpg converted but that is not the problem since the car acts strangly on gasoline.
They changed spark plugs because all cylinders missfired, after that I get really bad gasoline/exhaust emission smell in the cabin when I floor it. The car is struggling on higher speed and I can barely go over 130km/h (80mph). I looked at the air filter today and saw that it was broken on the edges. I think they forgot to check the air filter...but they told me that they smoke tested the air intake and could not find any leaks. I also changed the pcv valve with no effect..

I really don't know what do do more.. If not even Land Rover can help me out, what can i do?

Sincerly
Alex