Honestly. Use the OEM type plug. I suspect the misfires are the result of the plugs you used. Here is all the specifics as far as OEM spark plugs.
2014 Mazda 5 L4-2.5L
Mechanical (including Torque)
Vehicle Powertrain Management Ignition System Spark Plug Specifications Mechanical (including Torque)
MECHANICAL (INCLUDING TORQUE)
Gap
Spark plug gap (L3Y2 18110)
Standard. 1.25-1.45 mm (0.049-0.057 in)
New spark plug (reference). 1.25-1.35 mm (0.049-0.053 in)
Spark plug gap (LFJD 18110)
Standard. 1.25-1.35 mm (0.049-0.053 in)
Torque
Install in the reverse order of removal.
Tightening torque. 10-14 N-m (102-142 kgf-cm, 89-123 in-lbf)
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The code you listed indicate a leak or blockage. The first thing I would do is exactly what you are trying, smoke test. If no leaks are found, then we will break it down and start checking things. I attached a picture of possible causes of the code. Take a look through it and see if it helps.
Let me know what you find.
Joe
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Monday, March 16th, 2020 AT 9:05 AM