question on 2003 bmw x5 4.4

i turn on my ac and some days its cold right off the bat and some days it takes like 10 mins of drving to get it to blow cold? any ideas what it is?

pcv valve how hard its to change? looks orange and i need to take of beauty covers on valves and engine bay? saw a few videos seems easy

i also bought rear diff fluid and transfer case fluid i dont see leaks but after long trips
i hear weird noise going from park to drive or drive to reverse ? any body hear this noise as well?