Repeating coil failure - tricky

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Hi, I am writing in regards to my friends 2003 Mazda SP20 2.0L The car initially had the variable intake butterflies fail and the issue corrected, after a month of driving the car exhibits unusual running and idling characteristics, for example, the car randomly stall when coming to a stop and would restart after sitting. After driving several weeks with occasional stalling, the car starts to misfire and swapping of coils, deemed the shared coil for 1 and 2 faulty, the coil was extremely hot and a visual inspection indicated coil failure, as a bulge is protruding from the head. Replaced the coil and the car ran ok for a while until the symptoms repeated itself and the new coil had failed on the same cylinder as the first set. I have not had time yet to check the car first hand unfortunately. Are there any common issues that exude similar symptoms? I plan on checking the inputs to the coil and the PCM which from what i have read is located under the passengers footwell. Wiring was checked apparently for crimped wires and shorts. I believe it could be coincidence the coil failure occurred several weeks after repairs carried out in the area of the intake. Unsure at this stage. Thankyou