Engine smoother with full fuel tank, ~1/4 tank feels rough
 

Ive noticed the car 'feels' happier (smoother, less peppy on the throttle, less jerky) when cold in the morning if the fuel tank is full or the level is high.

When it runs low, in the region of 1/4 tank or less, cold driving just doesnt feel right. After its warmed up it seems ok.

Time for a fuel filter and/or pump change?

Do the Hatchbacks actually have a fuel filter/pump service interval as they are a combined unit?

Car is a 2008 STI Hatchback.