It's ok if you are on Twrp. This is what I did to get to this rom with nexus modem. Reboot to twrp recovery wipe dalvic 3 times and wipe rom. Download all the files below and install them in the order below. Note if you don't get service the first time you boot go back to recovery wipe dalvick again and install the modem and then kernel again. Reboot and you should be smooth sailing.
Note: This is really just a rehash of the instructions TexasEpic4g already gave on post #6. Follow the steps there and you should be fine. I just have all the links below of what you need.
Slim Rom ->
http://d-h.st/20v
Gapps(If you want Regular gapps choose Full packages and if you want inverted choose inverted Full packages) <-- Reference unjustified Dev
http://www.slimroms.net/index.php/do...gory/24-addons
Swap2Nexus Modem
http://goo.im/devs/effsi/Misc/Swap2NexusMdm.zip
Nexus modems I use KL2 but the most popular is LF2
http://xdaforums.com/showthread.php?t=1077168
Kernel
http://goo.im/devs/effsi/JB/Kernel/N....2Nm-0308m.zip
Note: some issues at least I'm having with the rom. I haven't been on a CWM rom for a while so I'm missing some steps or something to do most likely.
1) MMS broken- I used handcent as a temp workaround. I think the actual fix is entering the correct APN info
2) Voicemail missing- Just need to find the right apk to use.
http://xdaforums.com/showthread.php?p=30962032
3) Market can't download some apps while on 4G. I think this might be an issue of either the nexusmodem or dpi. Still trying to figure it out. My workaround is use wifi or 3g for now. Im thinking more the modem as it seems 4G is disconnecting right before the download can finish.