When I play on my server,off a different connection,I still see lag spikes with about half of the players..alive or in spectator.. although the server`s upload changes very little...I suspect the lag on non-cable modem servers is being caused the server`s hardware not being fast enough to update all the clients..so packets get dropped and everyones pings rise about 20-80ms for a few seconds every 2-4 minutes
So in a few weeks I am going to try a different router,motherboard and ECC ram to see if that changes anything .
PS My server is off a dedicated T1..so bandwith is not an issue.