These are basically strong engines but a lot can go wrong with them. Then need a fresh timing belt, tensioner, all pulleys and a new waterpump every 60,000 miles, then a cam-to-cam chain and tensioner at about 80,000 miles. Yes mass airflow meters can eventually start to fail and give erratic running. Temp sensors, oxygen sensors, flywheel position sensors too. And the 5 speed gearboxes are not as strong as the 6 speed twin shaft boxes fitted to equivalent SEAT Leon 20VTs, A3s and Golfs.