Re-opening with new info
Just emailed flat six innovations on this topic, and they seemed to think that the engine was toast because of the .5 second rattle when it starts up. They quoted me $18,000 for a new one. I emailed to them that the car was not necessarily making the noise when it's completely cold or hot, but that it does when it's in between, like around 110 degrees. This is in around 40 degree weather.
Flat six seemed to think that I was on the brink of a catastrophic failure. My theory is that when the previous owner changed the IMS bearing, he messed up timing, because camshaft deviations are holding steady.
Does anyone have the specs for the tensioner tension? Also, if it turns out that I take this apart to replace some chain ramps, and the main timing chain from the ims and the sprockets are worn, do es the engine case need to be split?