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Why not 4.d4,exd4 5.0-0,a6 6.Ba4,Be7 7.Re1,b5? White seems to get a good game with 5...Nxe4 6.Re1,d5 7.Qxd4,Bd6
5...exd4 is the main line for players rated under 2100, and it's almost never seen in games between grandmasters.
There's a fairly forcing line that really does look pretty scary though. It's been repeated in several games. It may be worth looking at to see where you can find improvements. In order to get better at chess, you really have to do your own work at some point, but here's a game to get you started:
7.Qxd4 is better than 7.Nxd4 Black will just get wasted.