Lag Spikes Please Help

[tristrum]

Hey,

So Since tekkit went to classic ive been suffering from some bad lag issues and its not just in multiplayer it also happens in single player, When I'm playing it has lag when i move to fast and spikes every so often and also lags when i open API's Like creative mode API and inventory API and also chests and all the other bits like that. Ive tried assigning more ram I've tried all sorts of fix's and so far no luck lol.

Any help would be greatly appreciated! :)