This question is a little tricky. There are a lot of factors that can play into slowing things down. Also the easy question, I always have trouble using IndustrialCraft II because it's on an entirely different energy system (EU) over (RF) like most other energy mods but there are ways to convert and IndustrialCraft certainly has lots to offer.
Now that aside, It'd be nice to have some computer specs (e.g. CPU, Graphics (if any), RAM,). I see you have Optifine and there are lots of settings you can play with to speed things up, mainly in the Performance Tab of Video Settings and adjusting render distance t reasonable levels to boost FPS.
Hovering your mouse over certain settings can give you a description of what it is and how it can affect your FPS. Look through these and find the options that best suit your computer
There are also mods out there such as FastCraft and BetterFPS that CAN but may not also boost your frames. Make sure however, if you install any of those mods, make sure to disable Optifines built in Algorithms if it crashes on start!
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Slickningkilla is the stupidest name I've ever thought of. So is the stupid skull gif.
I do have BetterFPS in there, and it didn't make a large difference. All graphics have been turned off and render distance has already been on 2 Chunks. FastCraft keeps crashing when I try to install it. Thanks though, this helped. (sry for not putting computer info in)