How was the A/F measured, is it possible that the O2 sensor was faulty? When my truck was on the dyno it was running at 11.5:1 and at 4700 RPM it out of no where jumped to 17:1. That was game over for that engine. Later on it was figured out a parameter in the VEC was wrong and was what caused this failure. Hopefully you dont have to go through the same.
There is your answer! Fuel delivery issues usually do not come with any codes. Take everyones advice. Before adding another variable to your issue. Check fuel pressure AND flow rate. This will be cheaper than a new engine. An SCT tune will not help if the fuel needed is not there.
Damn...that's a recipe for disaster...get that bish tuned before you have a really large paper weight