I have a 2007 tahoe and since new has had only around 20 to 25 lbs oil pressure at idle. I get a lot and mean a lot of these trucks knocking at work from car lots and 9 times out of ten it is carbon on top of the pistons. Saw u did seafoam I have had luck with it and not some times and always use gm top engine cleaner. Get it hot then shut it off and suck a can of that or seafoam down the brake booster vacuum hose and do it fast enough to get it down in 10 to 15 seconds and yet not kill the engine until the very end and kill it by sucking it in or shut it off right away when can empty. Let it sit an hour then start it and watch the smoke and hopefully noise go away as most times it does here at the shop. I dont know if you poured in the gas or did it that way if u did gas try my way and see what happens for you. good luck. Also make sure you dont have a loose flywheel or torque converter bolt or cracked flywheel!!!

 

Yeah thanks for the tip. I did put the seafoam in the oil but before that I had also tried the top end cleaner with no notable results.