Must admit that I have never heard of that happening. I have used the brake booster vacum line with no ill effects, but I have always poured it in slowly, carefully monitoring how the engine was reacting to it.

 

OH, and just to update the results of my original issue.... Obviously since I returned my truck back to stock tune before I took it to Ford, it cleared the code since I flashed the PCM so they were not able to diagnose anything. I drove around for about 100 miles on the stock tune and the CEL came back. I read on some other postings on here that cleaning the MAF sensor may resolve my issue. So I cleaned the MAF sensor with CRC MAF sensor cleaner, reloaded my performance tune, and have driven 4K miles now with no issues. (Took a trip to Florida so I really put some miles on it). So that was an easy enough fix to resolve my issue.