Strange behavior of the FI loop - diagnosis

Hey guys, need your help to understand. The truck is 4x4 2011with TRD SC and 2.85 pulley, DTLT, TRD CAI + AFE prodry. It is equiped with an URD MAF controller.

I was recording runs with my OT-1 and innovate AFR gage using logworks 3.0 to verify if the fuel pump was at the limit after a change of Y-pipe for a DT and want to check the impact of it on the AFR curve. And yes the pump has reach its limit. I've set the map to have between 11 and 11.5 AFR at WOT before the Y-pipe change and now you can see (2nd .pdf) the AFR is rising to 12 and i can't correct it with the MAF controller. So i will install the fuel pump i've bought URD.

My problem is about 1 recording i've done from 0 to 60 at WOT (see 1st .pdf). The TAC was off (auto LSD). I've seen the traction control has engaged at the start (20 mph +) but somewhere in the run, at the change of speed, i had something like a backfire with a large puff of smoke from the exhaust. Looking at the record I'm seeing 3 strange area.

1- A large area at high throttle were the ECU stay in closed loop (in 1st gear) so the AFR is high (lean) for a part of the run.

2- An important closing of the throttle opening (just before or at the gear change in 2nd) with a fall of AFR reading (rich). I think it's at this moment i've heard the backfire. Maybe it's the fuel pump limit in small gear? Maybe a protection from the ECU? Yeah ,pump will be change soon.

3- There is a flat in the MAF reading i can't explain. Is it the reading limit of the MAF probe capacity ? Is it a choked flow, there is simply no more air that can go trough this opening (intake system) at this pressure? For this one i will be surprised but i'm really curious about this one.

I'm a bit worry about that and don't want to do damage the truck. And i'm the kind of man that need to understand. I need yourlights.

The 1st pdf is the record of the problem - strange behavior.

The 2nd pdf is the run I've done for my map at WOT in 3rd gear. On this one you can see the AFR going from 11.2 to 11.95 cause of fuel starving.

So waiting feedback from TW gurus.