Flat-Four

Can anyone help?
My version 5 STI starts and runs fine. When I accelerate from cold its fine.
However, when it gets slightly warm it thinks for a second or so before it goes.
I have just had the car serviced and all filters changed, plugs etc. also just been stung £80 for some magnacore 8.5mm leads.
Next step must be the coil pack but don't want to spend anymore dosh.
Does nayone know what the resistance across the coils should be?
Its a diamond FH0161 12V
Cheers