Those peers just have faster connections than you.
Also, are you sure you didn't accidentally misread something? For example, did you perhpaps sign up for 5Mbps service but mistakenly read it as `5MB/s`?
One byte contains 8 bits. Conversely, 8 bits equals one byte. So 5Mbps (megabits per second) equals:
5Mbps/8 = 625KB/s (kilobytes per second).
If you made such a typographical or reading error and you're really getting 490KB/s rather than 490Kbps, then this is more or less the fastest you can possibly expect, probably.
As you know, ISPs work on a `best-effort` basis. So if you have a plan rated as `up to 5Mbps`, then this can be equivalently expressed as `up to 625KB/s`. If that's the case, then 490KB/s is very close to 625KB/s so you can't really complain, since you're getting very nearly what you pay for.
But yeah, there are some things you can do to make sure you get the maximum speed your line can support a greater proportion of the time. Here are some tips:
1) Limit your upload speed to ~80% of your maximum line upstream (eg. if you had max upstream of 40KB/s you would limit it to 32KB/s). Remember to set the speed back as high as possible when you finish downloading so that you can seed at full speed though!
2) Use uTP only when you're in the right type of swarm. Set bt.transp_disposition to `10` for uTP-only. So if you're connected to lots of peers who have fast connections but are throttled on TCP, this will let them upload to you at more or less full speed. For example, if you're connected to lots of Japanese peers who you think may have 100Mbps connections but are artificially throttled on TCP (eg. plala or OCN customers), use uTP and they may be able to upload to you faster (of course, they still could have limited their upload speed in their client, but if they didn't, uTP will help significantly).
3) You're not throttled by your ISP, since you're getting close to your maximum download speed. So uTP won't really help you on your end. Therefore, only use uTP when you think it will help out the remote peer to upload faster to you. If you're in a swarm where there aren't many peers using either the Mainline client or uTorrent, turn uTP off by setting bt.transp_disposition to 5.
Changing the port won't help unless you're using a blacklisted port like 6881.
Don't use the autoconfigure feature. You know more about your network than it does, so you can better determine the optimal settings. Although, if you really did mean 490 KB/s and not Kbps like I suspect, then you have no problem, since you're getting numbers really close to the speed advertised by your ISP.
Here are the combinations, by the way, for bt.transp_disposition: http://www.tmsnetwork.org/blog/%C2%B5torrent-utorrent-bttranspdisposition-values-explained
Good luck.