IMHO
A rolling road day isn't the best way of diagnosing your fault mate, ask them if they'll do you a diagnostics session where they can take their time and load your engine on the dyno at the exact point the problem is occouring whilst data logging via obd.
I have a loaner obd data logger you can borrow if you wish, it's small and can hold plenty of data
I can expand on the above when in back in the UK on Friday.
