206 + Cough and Misfire

2010 pejo 206 plus- general maintenance was done. After the oxygen sensor and spark plug changed, coughing started kicking between 1500 and 2000 rpm. He usually does it at lpg. By the way, the spark plugs were very dark when inserted. The masters said the coil without trying, but they say that if the original is not installed, it will not give you an endurance that it will cut after 120. The original price is the use of expensive subcontracting or this event. Thank you for your attention and help

There can be many reasons. Coil is also among these options. If the coil fails, the fault code drops to the system. I think you can connect it to an original device and look at the error codes.

measure the coil values. Measure spark plug values as well. Whichever cylinder spark plug has a problem, it also makes the cylinder injector and compressor test.