[blue62]

When your looking at data from an OBDII scanner or any diagnostic tool.... the data can be miss leading or meaningless if not taken under proper conditions.
Things like STFT's.... LTFT's...Pre cat O2 sensor readings ...post cat O2 sensor readings....those readings (all readings) need to be taken under specific engine load and or RPM conditions to be relevant.
Something as simple as intake vacuum test readings are meaningless if not tested under correct conditions and in the proper way.

I suggest you go to youtube and look up "scannerdanner" take the time to view as much of his content as possible. He is very good at diagnostics.. he uses oscilloscope type scanners most of the time...but you can learn good diagnostic methods from him and how OBDII data is used and applied and under what conditions.

There is a huge misunderstanding for most people concerning the OBDII system......
it's primary function is ....Catalytic Converter Performance....
Engine performance is secondary..... and tuned to Catalytic Converter performance needs.