It just speculation on my part, but it may have combined with some intake leakage on the left bank, and did it in.
Usually one set of dyno runs is sufficient for remapping to get it to within 95% of target. If the air fuel ratios are severely off, as is typically the case with Autothority's MAF chip, it may take a second set of runs for final tuning. Here's a thread on the same setup which shows the before, and after results with two tuning iterations. More power was actually achieved with less ignition advance by correcting an overrich condition:
Looking for fabspeed catbypass dyno results
MAF is only worth it if done right, it's just another component like a piston is to an engine, otherwise you are better off with just the stock flow meter and a chip. The quality and power gains of a MAF is all dependent on the software and the person who developed it to make it work, and it needs a special dedicated program. The stock chip, or any aftermarket chip will not work. Fine tuning for your engine gets you at the center of the bell shaped curve, otherwise you'll normally just be in the blue or green region.
Some owners are very happy staying with the Autothority MAF and a remap, others went back to the stock flow meter with a chip because they felt the power, refinement, and response was better. I like a MAF system, but only the Bosch HFM5 system you see on my site - with software and technology much superior to the 25 year old Ford hotwire setup. If you decide to stay with the MAF, I recommend contacting Professional Mass Air Systems, as they are the newly reformed company that took over Pro-M when they went out of business.
http://www.massairsystems.com/ Pro-M was the company that made the MAF for Autothority. A few years ago, they replaced the K&N filter with a dry media type cone to address the oil contamination issue that was so prevalent.