Engine Performance problem
2001 Audi A4 6 cyl Four Wheel Drive Manual 154k miles

hey there, hope you can help!
i have a 2001 Audi A4, 1.9 TDI. it recently had its fuel filter, oil, timing belt, AC belt and tensioner changed. Still giving problems.
It tends to occasionally cut out while driving, often in high gear at speed. (dashboard display goes off, it cuts out, power steering gets heavy, coasts to a stop. .
I can start it again and drive. )
scary experience. It has happened on bends which is really scary.
any ideas?
id appreciate your advice
Mary