Just NO ! they don’t belong on a GTi. And for people saying they avoid stone chips,absolute tosh. Stone chips don’t happen there. They happen on the bonnet and front bumper just like any other car. Flaps belong on corollas. Just my 2c on course. 
This is what I’ve found. Virtually stone chips on the lower sides or sills of my car without mud flaps in 3.5 years (certainly no more than on cars that’ve had mud flaps), but I’ve picked up a few on the bonnet and front bumper.
The subject of mud flaps crops up periodically on forums and will always divide opinion. Having had them on the 13 previous cars I owned over a nearly 40 year period, and now not having them on my current car, I wouldn’t bother with them again. Also, bear in mind;
- the front mud flaps on the Golf are very short, so are unlikely to offer much protection to the sill area, other than immediately behind the actual mud flap.
- VW mud flaps are made of a hard plastic so don’t flex if they get caught on an obstruction. When I owned my mk4 Golf, I caught the rear mud flaps against a high kerbstone when reverse parking up to it and one of them was ripped off the car as a result, damaging the fixing points into the wheel arch liner. Something to consider for anyone who regularly reverse parks up against a pavement, or has a steep driveway where there’s a risk of mud flaps catching on the ground moving from driveway to roadway.
As said, it’s a personal choice, but I’m a ‘no mud flap’ convert.
