Nasty engine stumble under load with highest premium 98 on top of 91

[Steptoe's photos]

Now that I am geared up to be able monitor two power circuits  (main relay output for the injectors + ignition switch and fuse No. 11 for the coil power) while driving, not only does it start, it does not miss or stumble, or carry on while revving it in the safety of my yard.. A moment to name the beast, for a reason ....