TomatoUSB

Hello! I recently put Tomato (The AIO here, not allowed to post full links: K26RT-N/build5x-132-EN/Asus%20RT-N66u%2064k/) on my Asus RT-N66U (D1). I just set up the wireless security and didn't mess with any other settings. I do not seem to be getting as fast of speeds as I should be wirelessly. My modem is putting out over 300 Mb/s as are the LAN ports on the router. However, when connected wirelessly standing right next to the router, I cannot even break 20 Mb/s speeds. What is going on here? Any help is appreciated, thanks!