RookieMaster

The only official tekkit client which includes EE2. Is tekkit classic.

You see. It has to be a golden pipe connected to the teleporter. Not the wooden.

Have you extracted everything from the zipped Server file. Because normally it is included in the zip/rar file.

Tekkit classic supports 1.2.5 Bukkit plugins. No later due to it not being updated to later version of minecraft anymore.

Tekkit Classic. It is the first of the tekkit Series which supported Multiplayer and Bukkit. It is not being updated due to having most of the mods on it. Most of them working and stable. And it has the latest EE2 Final we can say.

First of all. What type of lag is it. If it is when you break a block and it only disappears after some time. Then it is part of the server lag. If it's FPS drop. Then it's client lag. Servers can have lag problems due to few causes (RAM Problems, Server not been rebooted for some time may cause it, CPU Can't handle the server overloads, Loads of players) It doesn't matter if you have a 100mb/s Internet. If the server itself either has a slow internet connection or has overloads. Then it's not your computer problem. It is the server. So it doesn't relate to the client or your computer then.

Check if the server is not read only. If it is. Disable that. Also check if the redpower config exists. '/jar/redpower/redpower.cfg'. Also see if you are running as admin.

Tested. Confirmed. Running on a 4gb ram and java 64bit. Limiting it to 512MB does prevent lag. But due to limitation it can have a minor higher chance of crashing. Confirmed while using Memory usage of 512MB preventing lag but crashed after 6 minutes on the performance test map. On 2 GB. Had some FPS drop rates and lasted for 8 minutes. So it's not a big change. I still suggest with 512MB. But if running loads of machinery which require loads of ram (Singleplayer) Then i suggest a slightly higher than 512MB.

On the launcher. Select so it would use more of your computer RAM. It's in the launcher options when choosing modpacks.

Try updating the launcher. Or using a different type of it (.exe or .jar)

You can always turn off Matmos. That helps.

First of all. You have to find the modpacks for that version of Modpack and Minecraft versions. Second. If you want it multiplayer. Then i suggest going to add custom ids to it so it wouldn't overwrite with other ones and as well as get the server to have the same ones.

Try to backup your tekkit classic and reinstall a fresh one by deleting the old classic game data.

Did you attempt to backup your tekkit classic game. And reinstalling it?

Check your server.properties and see if gamemode is set to 0. Second of all. You can add a whitelist to the program. Third. You can Ban the people who are using gamemode. Fourth. Like rcmaehl suggested. You can use his patches for the issues.