2011 Denali 6.2L No Oil Pressure

[engineer_gregh]

I have a 2011 Yukon Denali that I bought new in 2010. Its always seemed to have piston slap when its cold but goes away as soon as the temp gauge reaches the 1/4 mark. In December I was at 99K miles and decided to drop it off at the dealer to get their opinion before it went out of warranty. They changed the lifters; it didn't really change the noise. Now at 104K miles I lost all oil pressure today as I was nearing my house. Any one else had problems like this out of their 6.2L engines? Any advise is greatly appreciated.