White smoke while starting up Nissan NV2500

I bought a 2013 Nissan NV2500 V8 with 60,000 miles on it several months ago and after a few weeks I went to check the codes and got a P0303 which indicated a misfire on cylinder 3. I was advised to use seafoam in the gas tank to try and resolve the issue and I did that but I also decided to change the spark plugs to see if that would fix the issue, I changed them all and a few of them had ash deposits http://thezenvan.com/images/IMG_0061.jpg. A little while after doing that I started to get white smoke on startup, at first I thought it was just a side effect of the seafoam but it kept doing so for a few weeks so I decided to do a block test to make sure the head gasket wasn't the cause and the test showed it wasn't. I also changed the PCV valves to make sure they aren't the cause. I also did a wet/dry compression test which came out fine https://i.imgur.com/OhZ4RXc.jpg, there were differences between the wet and dry results but they seemed to above minimum. There is oil being burnt because and I periodically need to add some. I tried putting Marvel Mystery Oil and doing an oil change too.

At this point I have no idea what's causing the issue, the warranty expired on it so I want to see if I can fix it myself. Any advice would be appreciated, thanks

If the smoke is actually more blue, or is definitely oil, then burning oil only at startup after the engine has been sitting awhile is typically indicative of leaking valve stem seals.

-Rod

That's what it seems to pointing to. The smoke is white and smells like oil and I do have to top off the oil every now and again.

I was just hoping for another solution besides having to take apart the engine