Have the trigger pin channel and even the trigger pin been polished to remove any rough parkerizing coating on their surfaces?
What size gaps do you have from the end of the trigger pin sides, to the inner sides of the receiver void walls?
Was the FCG installed dry, lubed with CLP before it was installed?

In regards to the trigger pin channel, lapping compound and Q tip on a drill works well to remove the channel parkerizing and smooth the surface.  On the trigger pin, same/same, while you want to leave the parkerizing on the ends of the pin where they will be riding in the receiver channels.


Next up, with sear of hammer smoked with a marker so you can dry fire the rig to see the rub marks, what is the engagement distance of the trigger sear to the hammer sear and is the engagement square to the end of the hammer sear.  
Also front side of trigger, how smooth is it,as well as the trigger sear surface?

On a stock FCG, when you are pulling the trigger, it will slightly lower the hammer until it release, so rough surfaces, and even over engagement of the sears will cause the harder pull of the trigger.


As for reduced tension hammer and trigger springs, not needed, since 5lb trigger that breaks crisp, is much better than any trigger that has a great deal of creep with lighter pull instead.

No worries, and double check the tail of the trigger, to make sure it not binding up on one side of the selector U channel side wall in fire  as well.