aftermarket billet impeller is just a part made to sell and make money on. has nothing to do with needing it. ive never changed any impellers. And that includes a 93, 96, 97, 00, 03, 04 banshees
so if 15-41 pulls easier then your gearing is fine?
If it was me id run 3 stock with the 3 in now. if that didnt work id run all 6 stock. imo simple as that.
Then adjust your lockup weight accordingly.