I have to disappoint you. Pump shot can`t be disabled.
My theory is that you have really lean condition at high rpm. Maybe you have 15.5-16 AFR. What saves you from engine blow is restrictive intake. Really low spark advance and high gears, low weight. I guess engine power suffers alot too. You get some constant 3-4 degree retard, where it comes from.
As you can see your AFGS from 5000 to 6600 rpm change only from 190 to 220, which is really low. At 6400 you should see 320-500 AFGS depending on engine power. Either your Maf is shot or there is some tune issue. Try scaling upper maf table by 20% and see what happens.
It is really important to keep the spread between cells from stock table. So you dont adjust single cell but scale the whole region.
When you tune MAF with wideband at steady throttle, you will get nasty tip in stumble at low rpm when you nail it. Narrowband tuning with closed loop enabled, masks that condition and considering lower weight is normal that you don`t get that lean. I have monitored wideband at tip in and jumps to 16 afr momentary, When you get around 17 you can feel the stumble and misfire. ARound 15.5-16 is not felt. At 13 AFR, power suffers. I am still trying to find the perfect point where you make max power.