My apologies if this has already been discussed.
I have a VAP Tuned 5.0SC with a lower pulley swap in my 2016 XJL. It was running great for about a year after the VAP mods. Recently, under hard acceleration it pulls like a bull all the way to the point it shifts and after the gear change the engine immediately begins to buck like an angry bull. Usually it will go away after I let off the throttle, but occasionally it will continue, like it is running on only 6 cylinders, until I shut it off and restart it. --- Additional details -- This is in all normal driving mode. Not in "S" on the gear selector or in performance mode, just normal engine mode and in "D". I haven't tried changing any of the modes yet as I'm afraid the additional stress may be worse.
Thought?

 

could be a weak injector or coil causing the misfire - that is why on restart it is fine as to save the engine the misfiring cyl is shut off until restart - had the same thing with VAP tune initially, but at WOT at 6k+ RPM only, Chris backed it off a few percent points and all has been well

 

That makes sense. I'm going to try a few things over the weekend, and send a note to VAP if it doesn't go away.