On previous bikes with aftermarket exhaust, I've always noticed more/heavier backfiring with the insert removed. Especially on bikes that run lean already, an more "open" exhaust is not necessarily the best.
For example on my Ducati I had a very open custom exhaust... No insert and loud as hell. However when dynoing it, it hurt performance. I installed a baffle and performance improved. This is an extreme example with a crazy loud and open exhaust.
I think you will notice more backfiring with it reduced, but nothing extreme.