hard to start
 

My car is Mazda3 2004 2.0l. I have problem about the car, which is hard to start. There is no any error codes showing up from scanner.
After sitting for long time, car needs long crank time to start such as 3-4 seconds. Yet, Car always starts. If i press gas pedal, crank time decreases.

Before starting, key is on about 2-3seconds, then key is off about 2-3 seconds. I will repeat this 3-4 times. Car starts perfectly

When gasoline in tank is low, car starts harder even if engine is warm.
After i cleaning Maf and changing spurk plugs and adding fuel cleaner, hestitation is nearly gone, also cranking time is smaller. But it is not still like a normal car.
My mechanic measured fuel pressure 31.6 psi, which is not so far than expected value, 36psi. Reason seems fuel pressure, filter or regulator. But, I have seen 2 different service reports about fuel pressure. One of them says that hold pressure after 5 m. should be 29 psi least. Another says 36.2 psi. I am conflused.
Also, i saw coolant temperature is 167F at idle when engine being warm. Ambient temp is 5F, I think that thermostat is misfiring. But, this is not reason for starting
i am open to discus