my octavia 1.9 diesel has just started to what i can only describe as chuggin more at low speed or when i first try to accelerate hard its fine at high speed the other day i thought i could hear like an air noise from under bonnet please help me again thanks

Is it a normal diesel or a turbo diesel?

Check the air filter box etc. for any leaks

On a turbo diesel check the hoses between the turbo and the inlet manifold for any leaks (you would probably get a light come on if there was a large leak though)

The other possibility is the dual mass flywheel is on its way out, this makes a chugging noise if the revs are too low for the gear you're in and you try and accelerate