The 'grace' here is not the collection, but the grace and favour shown to the poor in the gift. Instead of Paul having to press this grace on the Macedonians, they beg of him the grace and fellowship (koinonia) of the administration; that is, to be the instrument (though an apostle) of its manifestation by them. The 'grace and fellowship' is the active exercise of grace towards the Jewish saints. This they begged of Paul. (See ver. 19.)
'So that we were led to beg,' 'leading us to beg.' 'So that' states the effect produced; the tendency of the grace among the Macedonians he had been speaking of.