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 no engine management light on so suspect its not the MAF.
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.
Cheers

G17 NAT

I would assume that there would be an engine temperature sensor that gives a signal to the ecu. Might be a good idea to start there - check the connections are clean etc. Then measure the resistance etc across the sensor. I'm sure on here i have seen the values of the sensors somewhere.