I own a Ford Focus Mk2 (2007 model) 1.6 ti-vct that was converted three years ago to a Plug-N-Drive LPG system. About a month ago I noticed a whining noise. Took the car to the LPG fitter and was told that the fuel pump was failing due to having no lubrication from the gas because it was often below the 1/4 tank level. So he replaced the gas pump with a Bosch one and cleaned the fuel system by ''blowing''' it. The engine worked better, but still had rough idle so I cleaned the injectors by ultrasound. It turned out two of them were clogged (on two central cylinders)

Now there is no rough idle issue,only a slight hesitation when I hit the gas. There is also a slight vibration at 1600rpm and mainly at 2200rpm coming from the engine that goes away in the rest of the rpm range. The car also seems to have a ticking noise coming from the top of it (cylinder head?) that I think was not there before. Any suggestions on what I should do to protect my new gas pump and my engine in general?