Mazda 5 P0101 can't find the problem; where is the most likely place for an intake leak?

Question

I've already replaced the MAF sensor, cleaned the air filter (K&N) and checked the wiring...

Answer 1

P0101 MAF circuit / range performance problem

For a intake leak to set a P0101 , it has to be right at the MAF sensor air duct to the  throttle body, If there was a vacuum leak at the intake , This  would set a lean  code condition. You can have a 02 sensor set a P0101 only if there is exhaust leak right at the front 02 sensor.