Have you, by any chance used some 'Super HD Modifications'? With Super HD, I mean ones that are +512px who are not supported by GTA:SA nor. SA-MP. GTA:SA is capable of running 128px at max, and SA-MP increases the limit to 256. However, this bug can be resolved by either getting a CLEO Streamfix(512.cs or Higher), or an .asi streamfix(that one supports 256 at max, so it's useless with SA-MP.)
After re-reading the topic, I understood your means. Argonath, unlike any server, is mostly crowded at everywhere, Idlewood, Market, Commerce, everywhere in LS. LS is a place where many cars, trees, players(consider their mods too) load which are loaded in less than a second. That's normal, it could be because of your CPU's Usage level, or the mods, and it could be caused by the players' mods.