Hey man, I stumbled upon your thread here and decided to finally join the forum so I can give you my feedback on this.. I'll explain the stalling issue that I fixed on my denali.
I read the first couple posts and replies, and skipped down to your most recent posts so I may be repeating what someone has already said.
I recently bought an 07 Yukon Denali.. the seller disclosed that it stalls when at operating temperature randomly. He had a shop try to fix problem, they replaced fuel pump and who knows what else but was still stalling. As we talked about what the cause could be, he mentioned forums and some people were saying "just change the oil" to fix the stalling issue... we had a little laugh about it as to say it's obviously not the fix.
I drove it home the next day, was supposed to tow it but decided to take my chances first, drove it very light on the throttle, made it all the way to the back lane of my house where it finally stalled and would not start.. I checked fuel pressure, had plenty and still no start. Scanned it and got the code you mentioned "camshaft position timing advanced"(I forget the actual code number and description as I type this).. spent that night online, and by the end of it I read and was convinced by a few posts to change the oil.
Then it all clicked in the next morning, took a while to remember that the 6.2 that started in these trucks in 07 were built with VVT. The vvt cam phaser that is bolted onto camshaft operates using oil pressure to advance/retard the timing during acceleration/deceleration. Your engine with the low oil pressure cannot operate the cam phaser properly.. accelerate, oil pressure goes up, cam timing advances, decelerate rpms go down, cam phaser does not adjust timing properly, engine stalls.
I changed the oil, used 5w30 synthetic and lucas oil stabilizer synthetic, hasn't stalled once since. My oil pressure warm sits around the "quarter" mark, and climbs to the half way mark on acceration, not sure the actual number, haven't bothered to check.
So.. these early engines I hear may have had cam bearing issues, they wear, lowering oil pressure, and just general wear of the engine will have the oil pressure lower than when fresh/new. It's plenty of pressure to lubricate the engine in general, but not enough to operate the VVT properly. And yes the oil pump pickup tube o-ring can be an issue. I worked at and engine shop years ago, a shop we sold a reman 6.2 used the original pick up tube and didnt bother to change the o ring. That engine had super low oil pressure, we said no way its from our workmanship, tight clearances and "spin tested" before being shipped. We asked about the pick up tube and o ring, they admitted didnt change it, we said it's gotta be that, they r&r'd it and sure enough it was crusty like a cheerio.
You could run a 10w30 oil with lucas and it would be just fine, no harm in using that weight oil even though the oil cap says 5w30 and thats what recommended.. 10w40 would even be fine.. which I say would be equal to running w30 with lucas. Or stick the 5w30 with lucas like I did and it's working for me.
Well I'll leave it at that for now considering it's a long write up I just whipped up at 1:30am.. looking forward to being part of the forum from this point on..
Let me know what you think!