running lean?

So how can you tell if you’re running lean? I want to get and A/F gauge but I would like to have and A-pillar pod first and I might not have one for a while (if I can find one) with the new intake I am getting a lot of CEL and I am starting to worry can a tech pull the code from the ECU and does it have any logging capabilities? Since I have my HU moved up to the Gauge pod has anyone put the gauges where the old HU was? Maybe EGT, A/F and another with a S-AFC mounted below or a valentine one (drool).