Brakes first, performance second. Especially as the standard brakes are not considered the best unless they are perfectly well maintained and not sticking.
BUT I think you already have the 9239 anyway. None of the standard chips are performance upgrades per se anyway, they are just "different". Find someone local to you (where are u?) with an elanscan and find out for sure what you have.
You will only get a performance upgrade from the ECU by fitting a mountain chip designed for your specific promid (9929, 9930 9239 etc), as explained on the mountain chip website.
La vie passe vite: vivez la avec elan(s).
Elan S4 DHC 1969
Elan SE turbo 1992
Emira 2023
MB E250 CDi coupe 2013
Boardman Endurance SLR 9.4 disc 2018
Rapido 746 2010
Lotus Evija Danish edition