Before changing the settings on the cm927 from past experience i would first get someone to check that the low gas rate is correctly set in your boiler. This is a common problem with most combis. If your low rate is set too high then the output could be much higher than the 11kw it should be. I would also guess that you may have a low heat requirement aswell. If your home has less than 3 bedrooms then this heating output would be too great and then you will need to alter the cm927. I ahve emailed you a copy of the install guide on how to alter the necessary settings in category 2. ot change to 4 mins
cycle rate to 3
cycle rate to 3