Pulsing at steady speed

Hello. 

I have a 2015 octavia 1.6tdi 4x4 estate driven 150.00 km.

When driving and maintaining a steady speed in the range of 1500-2000 rpm it is like the car is pulsing. Just like the car accelerates and decelerate non stop. It has been doing this for couple of years now but is getting worse.

1000km ago I changed the timing belt, rollers and water pump I also changed everything in the clutch.

I have a feeling it is probably fuel filter related or maybe injectors.

Does anyone know this symptom.

Best wishes from Iceland 🇮🇸