There is no need to be aggressive. This is free help.

And none of us believe you . Actually, nobody else has that issue. Additionally, your question was about transmission having low speeds, which it doesn't. You also asked if we think you missed something, and we do.

See, this is why we have trouble with your feedback. If your PC has the same port then you can't use it on the N900 at the same time, unless you redo your router configuration each swap, then reboot the router for the connections to reset and the new routing table to have effect, which is something you never mentioned.

If not reboot, at least wait a while. Few home routers have instant routing, especially if you reuse the IP.

How did you test the port? Used the PC and assumed it worked or did you try to telnet from the outside?

That's because we have the same device, same Transmission and basically the same torrents. Your setup is the only unknown here.

Also, there's the question of your PC's configuration on the torrent client.

When working with external peers, sometimes the limits are very low, about 1k. A PC with a unconfigured torrent client links about 50 peers, and a broadband like mine about 600 (100M/s). Transmission is limited to 15 global in settings, that could keep your speed low if some peers don't cooperate.

Try increasing the limit (make sure you revert the setting if it doesn't help).

Also, try to debug your up/down link, try downloading/uploading a large mail attachment, see how long it takes.

You could try a telnet from the outside to the forwarded port, make sure it's correctly set up.