EGT alarm in Power descent

Hi all,

Apologies for yet another EGT question in the fourm but I've had a good search and general read around and I am still confused.

I've got a reoccuring EGT alarm (900c+) from cylinders 2 and 4 on the flydat that only occurs during power descent (RPM approx 4600-5000). 1 and 3 stay below alarm limits and all remain below 900 in the climb/cruise. Engine is a older 912 with 900hours. It lasts long enough for me to notice (30secs-1min) but drops when i raise the nose and airspeed bleeds off.

I first noticed this a few weeks back in a descent  when the OAT started getting colder (Uk based) so not sure if that has something to do with it. Carbs have been overhauled a few months back, new spark plugs this week and new floats and carbs synced using carbmate alongside changing fuel filter etc. Temp probes seem to be working ok and as I said it happens on both at the same time with no obvious rough running.

I only use Ul91, normal K&N filters.

I know some people don't read too much into EGT's but welcome any thoughts as I'm a little stumped. Maybe it's something, maybe it's nothing but I don't think I'm flying the aircraft any different the last few weeks that would easily explain away the alarm so would appreciate any thoughts.

Thanks all.