it does NOT overfuel.
Stick it on instant MPG setting and boot it. You will notice it only goes down to about 30mpg instant even on full throttle. It only allows about 30 to 40% acceleration on my estimate.
NO damage whatsoever is caused by limp mode as there would be sod all point in the VAG group making cars go into limp mode if it did more damage.
Limp home mode is just that. Limp a bit, crap power, but SAFE - the most important thing.
I ran my car for 3 weeks+ in limp mode when I did the pd130 conversion until I twigged I needed the pd130 boost sensor as well....