Poor wifi speeds.

I've been having problems with my WiFi. I'm on a 20mb connection but I only get 2mb. I have reinstalled my phone and done updates but it doesn't help. Right when my phone boots up I get full speed then after about a minute it slows down. I have removed apps that I feel might be the problem and even used an app manager to kill all running apps, but this did not help. I even updated my radio's and installed different ones. Has anyone had any problems like this or have any advice. I'm running the newest Sprint os.

Thanks