This is what you need to follow
1. Download the signed zip version of the kernel and place in external sd.
2. Boot into recovery and choose "apply update from external storage".
3. Choose the file you downloaded.
4. It will do the magic.
This will give you root access and yes apps like TB can be used. Also you will get CWM and it's a safe kernel too.
Dude he has done everything correct i know.. The v.3.99 of ics kernels are not built correctly when you flash them in stock ics recovery they always give a verification failed error.. But the older versions are ok to be flashed in stock ics recovery
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