It's definitively load related. Curiosity got the better of me, so I changed went back to the normal OL fuelling and tried to change the load scaling instead. Changed 3700 to 1.25. Both stock and OTS has 1.3 already at 3200 rpm so I thought it would be okay.
Oh boy! It felt like the engine was running at half power. Never has the car felt so sluggish!:
It did however, correct the dip.
It used to be between the two yellow lines. Obviously it throws the whole MAF scale off as well and now it's running insanely rich.
http://datazap.me/u/tor/205?log=0&da...mark=3487-3510
To top it off, I heard for the first time real audible knock. Didn't sound like "ping" though, rather a sizzling sound. Ptjuzzzz combined with a noticeable bogging down. And this was under light load as can be seen in the log:
Next up: Reverting to standard loads and OL fuelling and forgetting about the dip. I am going to have to go with Wayno and aagun on this one, that dip is probably just somehow a wrong representation of what is actually going on in the combustion chamber.
But hey, learning by doing... It was an interesting experience.