Black ops lag xbox, please help?

Got a new ISP this week, upped my Internet from 10mb with previous company to 15 with new.

All of a sudden I cannot play black ops online, every time I start getting shot I lag.

It's almost as if I lag when someone is looking at me, if I shoot someone in the back I'm fine, but in EVERY gun battle I lag.

Also every killcam is them looking at me, and then me immediately dying, the killcam lags whie they are shooting at me. Almost like a frame rate lag described by computer users.

Same router, I have tried port forwarding needed ports since the lag, didn't help. The Bly things that have changed are my modem and new ISP company. Arris 602g modem and ISP is wow Internet and cable.

I don't know how to fix this problem, tips for asking the ISP to change something or Xbox settings would be appreciated.

Also speed tests show my iPad and computer can use the full 15mb download and 1 mb upload. And I have also tried hardwire connection from Xbox. Not sure what else to do.

Thank you