Have just fitted a K&N panel filter to my 1.9 TDI Octavia. Result it revs more freer but on taking foot of accelerator it does not slow gradually down rather goes flat almost immediately. -as if back pressure has been reduced.

Is this normal?

From what i've read the K&N makes little difference on the 1.9TDI without a stage 1 remap, that said a lot will depend on the state of your old filter, if that had half the sahara in it then you will notice a difference but from a clean filter it seems the difference at stock is minimal.