I totally agree with OHbowhntr and everyone else about correct tuning. That being said, your bow can be tuned and you can still be hitting in different spots. A piece of crap broadhead won't fly straight even if you're tuned correctly. I had this same problem when I got my new Mathews. It wasn't until I tried several different broadheads that I was finally accurate with both field tips and broadheads. It's the same with everything else bowhunting- you can get advice from everyone, but it really comes down to YOUR setup, and what YOU'RE comfortable with. Everyone is different. Your buddy might have the same bow, strings, arrows, etc. but shoot a different broadhead to get the best accuracy with his setup.
I would say once your bow is tuned correctly, try different broadheads. I tried Grim Reaper, NAP, Maniac, and finally 3 Blade Rage. The Rage is what I finally decided was best for me and my setup- absolutely accurate. And you wouldn't believe the hole they've blown in 2 deer I've taken. But they may not be best for you.
I know it costs money to try these things, but confidence in your accuracy is priceless. Find whatever works for you.