Wireless Problems with iMac

[Cafka]

Hello everybody,
In the last few weeks, my iMac's internet has become frustratingly slow. My iPhone and macbook work perfect on the network. I have reset the router/modem/computer. I've upgraded the firmware on the router. I've added the 4.2.2.1 and 4.2.2.2 dns servers and I've turned on dhcp as well as tried static ips.
I get bursts of information to the point where it stutters like an old 56k modem. I've also run a speedtest and pingtest which all came out fine. Additionally I've tried to run the wifi diagnostic utility, but I can't figure out how to use it except for see my noise to signal strength(which is good).
What are some other things I can try to keep me from throwing this computer out the window?

Thanks,
Tom

 

[satcomer]

Follow the steps in this blog post and see if it works for you. Remember to reboot to rebuild those files.

 

[Cafka]

Thanks Satcomer, I renamed the preferences.plist file and restarted. It created a new one, but I'm still having this slowness.
Should I try renaming the whole systempreferences folder and reboot?