Strange. Unless you installed this manually then there shouldn't be any id conflicts. Anyway...
First, remove biomes o plenty, then open FTB, open a world, open your inventory, go to NEI options, and get an ID map dump. Then, look in your installation folder for the dump file. Close FTB, reinstall biomes o plenty but DONT start FTB. Now go into your config folder, open biomes o plenty, then open main.cfg (preferably with Notepad++)
Now, just change the conflicting ID's with ID's that are freed up. Finally, you should be good to go.