Donīt have too much knowledge about ECM, but here are my thoughts:
My first real experience with ECM was an increase of VIB levels that the operator wanted to be addressed. What we found were about four (prematurely) worn bushings of the LPT cooling manifold (CFM 56-5C4). Replacement of these parts brought the VIBs down. Amazing, I think.
Apart from this and many other "good" cases, we often had a hard time interpreting all the data.
And I can remember one case, when we had spent already so many thoughts on a steep decline/increase of several parameters - until we realized that we had locked out the bleed system under MEL several days ago... AAHRG!!!
Regards,
J. V.