I have a C230 2008 Elegance Model, 80K KM on the car, works perfect until couple of months ago after I got Gas , 4hrs into it, the Car started to misfire, endless jerks, losing power, went to the gas station, got High Grade Gas & STP Cleaner , drove it for like 10mins and car was perfect- drove perfect for another 2-3K & then happened again, went to the dealership, OEM scanner showed that Fuel Pump wasn’t in the range mentioned , the value was 2.3 in red, got it changed, again happened after 2 weeks, took back again, Cylinder 1,2,3 Misfire, checked Spark Plugs & the those needed to be changed, got it changed to bosh platinum & again today, went to full up high grade gas & the fuel needle was on Quarter Tank, below quarter to be precise & again the car started to misfire..

what could be the issue? Is it bad gas? Fuel Filter Clogged or Both? Or is it a Air Leak?
Any help would be appreciated.