Cold starting problem with my 2001 4.0 XJ8

[W5Plumbers]

My XJ8 is a real pain to start from cold, having to crank for at least 15 seconds++ then when she does fire its spot on on, running perfectly smooth. The problem seems to fade away when the car is warm, no errors on dashboard, occasional lean bank 1 & 2 which I clear with a scanner but this makes no difference in starting if it shows error or not. Can anyone steer me in the right direction as to what items I should be looking at (new air flow meter fitted as well)

Thanks