Even though you tuned your bow with field tips, sometimes it takes just a tad bit of adjustment to get broadheads to fly perfect. If your grouping well and have good arrow flight then you can just adjust your sights to your broadheads. If your getting incosistent groups, it could be you or your fletches might not be doing there job to steer the arrow. What kind of vanes are you shooting? There is a multitude of things that it could be. Just try and tweek it a bit and if that doesnt work try a different head like someone suggested earlier.