Deleting those racks will help a small amount:
They don't have cross bars, which is good. But don't forget that a vehicle rarely travels "straight" into the wind. We live in a world of cross winds, so on the highway those things are making more of a mess than you might think.
But we're talking a few percent difference - just a guesstimate.
I agree with randomfact: biggest, easiest gains are to be found in your driving techniques. Not discouraging mods (they help regardless of who's driving), but they're typically more work for smaller, incremental gains.