I have the same problem, but I'm not spiking like that. I noticed that since December, my MW3 ping has stayed at 20+ all the time, and before I upgraded to the R3, I always played in 11-13. Another thing is that the servers show Philadelphia, but MW3 does not have servers in Philly; they are in Long Branch, NJ, which does not make sense to me.
My speed is 2k down and 200 up. If I test with an Asus Rauter, my ping is 13, but if I test or optimize it with the R3, it is consistently above 20. Another thing that does not make sense to me .