Lag issues 3.1.2 - Server, computer or in-game mods?

[Syn]

Hey guys and gals,

Basically I run a Tekkit server for me and my friends (around 8 of us) on the following configuration...

Intel E3-1270 Quad Core (3.4GHz+)

16GB DDR3

120GB Intel SSD

1Gbps connection

CentOS 5.8 64bit running McMyAdmin (latest)

My TPS is constantly 20 and memory is never using more than 1500MB with no higher than 7% CPU usage upon monitoring it for several hours whilst playing.

Plugins: CoreProtect, Essentials (all), WorldEdit/WorldGuard, StopThatLag, LagMeter and Bukkit++ snapshot. The plugins are all using the correct RC version too.

Now the issue is it runs flawlessly, no lag at all and then suddenly when I look at the crafting page (ONLY the page that has timers on it on Large UI Scale) or place a timer (or a block like the RS Latches etc for example) it lags. It is not just me who gets these lag issues but other players too. I can edit with WorldEdit and do a hundred thousand blocks at once without any lag issues but those timers are doing it.

My computer more than capable as are theirs, I have tweaked my Java file and dedicated 8-16GB of RAM (My system has 64GB as I do heavy designer programs for work) to no avail.

I understand that the items can cause issues above but is there anyway that I can fix this?

Thanks.