100% CPU usage FTB Ultimate?

Server is running forgebukkit
Okay i have been running a ftb ultimate pack server for the 2 days now and there is 100% CPU usage there is allot of the lag but the lag can stop for a while then start again. There are around 10 people always one the server.

The server has a 2.9 GHZ cpu with 6 cores
currently 8GB ram dedicated just to the ftb server.

Im not sure why it is lagging but when I first made the server mystcraft was enabled I have recently disabled it.
Another thing I may have spawned in a few of those trees called the tree or time and tree of mining that says it could damage the world use with caution.
I have also noticed it tends to mainly lag when people are generating new chunks.
I have around 20 plugins all plugins seem to be working fine.
Another thing is from the dedicated server I set up multicraft on it to run the server and that says 100% CPU usage most of the time.

 

Go ask them - we don't support mods.