Will swap the plugs and the coil packs with my other car. I'm also wondering if there is anything or something shorted with the original tail lights, which have their typical moments, they are old and I've worked on them. Might swap them too. Maybe there is a short and again, my issue only happens when braking. The car just shuts down. It doesn't hesitate or struggle at all, no bigging, just boop, off.

Someone mentioned to me Torque Converter sticking, but the car doesn't have any other symptoms relating to this such an issue.

I'd like to get more data from the car and record live data if that might help, but not sure what tool would be best to do this?

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2003 X5 3.0i Silver (build 07/03)
2006 X5 3.0i Blue
1977 Ferrari 308 GTB
1994 Ferrari 348TS Speciale #14/15
1989 Ferrari Testarossa