slight idle issue??

[Fats]

Only noticed recently that the idle on the old girl is a bit rough but only when the side light\'s/head lamp\'s are on? It starts fine hot and cold but when I mot\'d it the co at tick over was 6%!!! and the wide band sits around 11.2-11.3,

First thought was compression, has anyone had this before?

She\'s on a single tub with all supporting mod\'s, injectors, intercooler, power fc......

cheers
Andy