On the highway it can be very quiet or a little louder depending on throttle modulation. But if your maintaining a steady speed you can hear it a little bit but I wouldn't call it a drone.
You can easily have a conversation with someone or listen to music which then blocks out some sound.
With the 3 mods I have this car flys! I was up to 120+ on the freeway this morning in no time. It's a fast and fun car. I love how you can hear the turbo and diverter valve blowing off now. The exhaust gives an awesome couple pops during gear shifts at full throttle.
If I get a go pro I'll attach it to the bumper and take a video.