My range rover p38 started missing,at first i thought it was ignition leads.I found out it was bad fuel in the tank causing the problem.My car had been standing before i bought it and after doing a bit of research on line it seems lead free petrol is a mixture of 10% or more of ethanol,this is where the problem is.When it is left in your tank over time ethanol attracts water and as the fuel ages it turns acidic,which in turn transform into a thick sticky tar like gunk in your fuel tank.I have cleaned my tank and replaced the fuel pump for a second time,but after starting my car after all this work it seems like it has got through to the injectors because it is still running rough.So now i,m going to have to take out the injectors and test them.So be warned about leaving your car ,bike ,boat ect with the type of fuel in.