Java Settings:
Version: 1.8.0_25 64-Bit (Default)
Memory Allocated: 2GB
I have always noticed that everything else my computer does when running any mod pack is laggy, especially web browsing. I have looked at the Mac Utility called Activity Monitor and that has given me some data that may be useful.
Tekkit Classic is using on average 25% of the CPU, 760MB of memory and it also says that of the 8GB of physical memory about 6.75GB is being used which seems like a lot to me, is this anything to go on?