You know youself Bill, different day different result that and vagcom is a piece of crap to log with IMO as alot can happen in a second or 1.3seconds sample rate it gives you, i have missed top end G/S readings before with it.
Why i am interested in the stack is because it is supposed to even out the air hitting the air mass meter, if this is the case a de-screened MAF should reading accurate figures.
Lucky my buddy had a tool for logging, i could get about 20 samples per second, so i will give this another go.
Here's a log i did tonight, nothing special, just a 3rd gear pull, but look at the sample rates once graphed
UH a Jetex and a BPi stack, now thats a happy little partnership, i never thought of this, thanks.
The filter with my stack is K&N