If your admin has access to them, have them check the server logs, and enable logging for a little bit if it's not already enabled, to see if that gives you any clues as to the problem. Also please remember that more memory is not necessarily good, what the server admin needs to worry about is the java or javascript garbage collection routines it runs. If you have 8GB running the modded Minecraft installation and have 7 people playing, it's probably doing a lot of garbage collection tasks. These occur because Minecraft constantly has to evaluate whether a loaded object or construct is needed in memory, and if there are a lot of them, the server starts taking them out, and can cause a lot of lag cleaning them all up. This can even lag a 8GB memory setup, due to the fact that you have 7x the normal amount of players a single-player world would have to deal with. I would hazard a guess and say that it's probably because people are doing a lot of exploring on the server. Or it's because someone is using a quarry or lag generating setup of some sort, and doesn't know it. Usually the server logs will tell the administrator what is going on behind the scenes, and they'll be able to fix the problem based on that and a bit of research.
Things to avoid: Excessively large amounts of entities on the ground. If you have a mob trap and items you don't want are simply discarded on the ground, this means they have to wait out a 5 minute despawn timer, which is bad for a server, much better to have everything collected soon as it drops from the mob, and sorted into a trashcan or other excess item removal device.
Large or complicated AE2 systems: I don't know how good your friends are at building AE2 systems, but be cautious as if they build a complicated setup, it can cause lag, if excessively overdone, it can cause a moderate amount of lag, which will contribute to your problem.
Inefficient item processing setups: If a system is designed to process and store items, it needs to be efficient at what it's processing, and prevent items from taking multiple trips through the same machines, and have routes that preferably favor an optimal design layout. If it's just a jumble of pipes hastily tacked together, it may cause lots of extra lag due to the amount of extra computations needed to handle the design. Always review item processing setups and make sure that they're as efficient as possible.
Chunkloaded fluid pumps: Believe it or not, this can be a major source of lag from the Nether. A lot of people like to go to the Nether and set up a pump to pull lava from the Nether into a dimensional teleportation device and use it to power their initial machine setups until they get more complicated options going. All of that lava being pumped out generates lag due to the updates needed for each source block of lava being removed. If a lot of people are using lava for power generation, it may be simpler to use a Creative lava tank and a transfer mechanism or alternative power sources. The admin would have to set up the Creative lava tank, and set things up so everyone can pump from it.
Those are just a few things I could think of off the top of my head, it's highly likely you may be missing a simple problem, which will of course require an equally simple solution. Hope that helps!
Cheers ...
BrickVoid
