What is the downside to ecu flash software?
I've been reading for years about ecu software modifications and upgraded chips for cars.
On this site I've read that certain ecu flashes can increase power and driveability and even decrease fuel consumption.
With all of these improvements I wonder why BMW doesn't provide software that maxes out all of these factors as standard, the obvious answer is that there must be some reduction in reliability.
So here are the questions; What are the downsides to a software upgrade? What does a software upgrade do to the way the engine operates, and what adverse effects are probable and possible to occur to an engine thus modified?
I have searched and not found what I'm looking for.
E90 Interlagos Blue, (Winter Beater) Bamboo Beige, M-Drive, EDC, PDC, USB 6MT.
Mods to date; Curb rash, Scraped front spoiler, Installed RAC Monolite RG63 Silver
1984 Porsche 911 Carrera Coupe (ROW)