I'm pretty sure the fuel distributor ("spider") on the Continental system is the same as on the Lycomings and if so, it is what controls fuel distribution at idle. There is a narrow slot for each injector that is progressively uncovered as the flow increases, so if one slot becomes partially plugged it will affect the idle flow. Once the flow increases to "flight" values the plunger pulls all the way out of the bore and from than on flow balance is determined by the injectors. Bottom line is that I don't think that symptom is related to anything else, and if the engine runs okay at idle it usually something with which not to be concerned. Just my opinion.
Gary
From: Dico Reijers:
I've just noticed that the #4 CHT /EGT is very low compared the the rest
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(see graphs taken at 1040 RPM idle). If I push the power to 1600RPM or bet=
ter, the CHT/EGT for #4 come up in line with the others.