The angled style exhausts pay homage to the supra. It was neccessary on that car with a big exhaust I.D. to clear the axle with the least restriction.
Now... about the airflow thing... your exhaust gases are under more pressure than the air around it, so you could point the damn thing anywhere and be fine. I believe the way you have yours setup is sufficient.
If you want to do something about airflow, install a diffuser.
But that's another project......