Ya, not an expert, just a keyboard jockey who likes looking at logs lol. From what I understand, the logic on our ECU is "torque based" (ie not boost, etc) and controlled by the "fly by wire" throttle (ETC Angle) based on a number of parameters. If the car senses its about to reach its target torque (as defined on a torque table), it closes the throttle momentarily and then opens again, etc. The tuner usually edits the torque target table based on what they see on your logs. I'm guessing the oscillation is from the engine flip-flopping between values on that table. I've been told this is normal and doesn't affect the power delivery (which I would agree with) and at most you'll just hear the whooshing sound oscillate.
Wow...that was fun! Very interesting logs! Definitely could see how much the charge air gets cooler with the meth and how much the timing the engine is adding to take advantage of it (almost 1.5 deg!). Its nice to see that nothing else is getting affected or pushed to the limit (ie boost is still the same, waste isn't working any harder, etc.). I did notice that the fueling (stft%) is different, with the meth logs needing less fuel. I wonder if that has something to do with the cooling effect that the fuel has? Hmmm...You are correct, I did post duplicates. I edited my original post and should work.