When placing or breaking any blocks near Mekanism's stuff (must be within your render distance) the game will lag or freeze for a millisecond. This also happens when a machine turns on and off a lot.
For example PRC being faster than crusher will turn on/off a lot. This dropped my FPS to 7 from 100. Note that this only happens when the machines turn on or off, not when they're running.

Did your PRC actually output ethylene, No matter what i did to the config mine would not output the Gas, i am aware the gas output is on the right hand side

I don't remember if they used to output gas in 1.7.10 but in 1.9.4 you have to set the pipe to pull the gas out of the machine.

So the actual pipe needs configuring. Maybe this is where i am going wrong XD
It used to be a case of setting the side to output and using auto eject

Yes indeed, you have to use the Configurator

90% sure this has to do with the way CTM stuff is rendered- CTM connections are recalculated and rerendered every time the world renderer updates which likely leads to some overhead when you have a lot of multiblock contraptions nearby. I'm too busy to do anything about this now but I'll look into some caching in the near future.