Like acceleration enrichment, there is also deceleration enrichment that is used to improve transient throttle response. It's good for exhaust fireballs in some very high performance applications. At the same time, auto manufacturers have been using "overrun fuel cut" since the advent of EFI in order to increase fuel economy. What it does is shut off the injectors completely under engine braking. That's why AFR gauges typically read off the lean end of the scale (20:1<) when decelerating with OEM injection systems.
On a side note toward the Dahlback Golf with a five-cylinder Audi engine....I love the sound of those odd-cylinder engines. The Group B rally Audis were incredible. The 1.5L supercharged triple Sea-Doos sound knarly too.