[AWSAWS]

Will a backend flash make any difference during an MOT?

I imagine that the BMS Race Flash only makes a difference at the top end and during idle the car will function as normal.

What are people's thoughts?

I think flashing back to stock will only take 2 mins anyway, so I think that is what I'm going to do.

[windymissile]

Will make no odds whatsoever.
What is it you are worried about?

WM

[AWSAWS]

Emissions...
But it shouldn't run any richer until high loads, I'd think.

[Aragorn30d]

So long as you've got cats present it will be fine.

Any decent tune will run the engine at Lambda 1 at idle and low/part load and will have no effect on the factory emissions at all.