Keg pressure ?

When you first pressurize the keg say with 20psi, does the beer obsorb CO2 bringing my regulated pressure down 5psi with in 8hrs.

If you pressurize a keg with 20 psi to purge the keg and seal the lid and then remove the QD, the beer will absorb the CO2 in the headspace. This will reduce the pressure in the headspace and make it appear as though you have a leak.

OK, so should I leave the tank on the whole time to my desired psi to maintain it, because I checked for leaks with warm soapy water on all the connections and I see no bubbles whatsoever.

Cheers, Scott.

Yes. For the best, most consistent results you want to carbonate and serve at the same pressure, which requires patience. First you need to determine at what temperature your beer will be carbonating at. Then determine what pressure you will need, at that temperature, to give you your desired volume of CO2. Lastly, you will need to balance your serving pressure with the correct length of 3/16" ID, thick walled, smooth bore beverage tubing. A good rule of thumb is 1 foot for every 2 psi of serving pressure. A balanced system will ensure foam free pours.