What about teaming with an ethernet cable and wifi, is the router/modem in the same room ?
What is your internet speed?
If you have 30Mb/s and above that's good enough for gaming, true downloads will take longer but you could skip teaming if Gamefirst IV is laggy for you. Or, if it's not too big of a deal you could reinstall windows and give it a try again with minimal programs.
Are you on the latest bios and MEI driver?
If you're able to use an ethernet cable, I could try GameFirst IV to see how it works for me, I never used it as I have 100 Mb/s download speed.
Explain a little more about the lag, do you mean fluctuation in download speed or whole system lag as in laggy mouse/games etc.. ?