WH Statesman Coil Pack

[PhD]

Hey guys,
Im getting wierd shuddering/misfiring lately, and ive replaced the leads, plugs and crank sensor and its still doing it - so i decided to test the coils... thikning maybe its that.. but they seem to be ok..

Ive read that the resistance specs are supposed to be, 0.3-1.5 Ohms on the primary coil (the underside of the coil where the prongs that stick out of the dfi module plug into) and 5000-7000 ohms across the secondary terminals (the ones where the leads plug into on the coil itself).

ive got the multimeter set to 20K on Ohms...
and each coil is:
6/3=5.60
5/2=5.49
4/1=5.60

These translate to 5600, 5490 and 5600 ohms right? - so these look well within range...

On the primary coils - they are each 1.2ohms - so it looks like the coils themselves are ok...

How do i test the dfi module if its working ok or within the right range?

On the dfi module - reading the ohms across the pins there i get 16.73 kOhms across each set of pins... is there some value there that they are supposed to be between?

The only things i havent changed are the cam sensor and o2 sensors... .. the shuddering is when under load and even at idle at the lights - but it comes and goes, some days it will do it - others it wont... any other ideas?