Unkown FPS drop/stutter problem

Hey,

I recently upgraded my old Acer craptop to a new Macbook Pro. I had tried playing LoL on my old laptop before, but it just couldn't handle it, however with my new laptop I realised I would be able to play LoL really easily due to it having high(er) specs.

I played LoL on my laptop for about 5 months, without a single hitch; I could run at high graphics and my FPS was a solid 60 all the time. However recently for some reason when I play my FPS will suddenly drop from 60 to 8 for a good 5 seconds and then jump back up. This happens very regularly in a game, around once every 2-3 minutes.

I know it isn't an internet issue. I have tried running all lowest settings but there is little to no change, the stuttering still occurs. I have reinstalled the game twice, I have repaired the game for any corrupted files, I have played with no sound on but this doesn't fix it. I feel like it isn't just a pure performance issue and that my laptop can't handle it due to the specs. This began ~after path 5.7.

Has anyone had any similar issues, and does anybody know any fixes. I can any spec info etc. Any help would be great as I had just hit level 30 before this all began and I really wanted to play ranked!!! :)

Note: I posted this in the Help & Support boards, put that is just filled with people raging about the tribunal/servers/elo hell so I didn't get a response...