My other car is a MINI!!!!
This happened to me on my old AGU. Does is still misfire when cold? Interestingly, mine would run fine for a few minutes when cold, then start missing once warm when boost went above 10psi.
I changed the plugs for brand new denso IK22's, and this didn't help at all. I spent months trying to solve the problem and replaced almost every other ignition part, only to find in the end it was the plug gap too wide!
New platinum NGK plugs in there gapped correctly, and it's been perfect ever since.