Download speeds slower on faster connection

[thesuffering]

Version: (Ex: 0.5.0 Final) 0.7.16
OS: (Ex: Windows XP SP2, OSX Leopard, Ubuntu Gutsy) windows 8.0
Install-type: (Ex: Windows Installer, Windows zip, OSx .app, OSx source, python source, linux repository, NAS package) windows installer
Skin (if applicable): (Ex: Default, Plush, Smpl) plush
Firewall Software: (Ex: None, XP SP2 Firewall, Zone Alarm, Norton Internet Security, Kerio) non
Are you using IPV6? (yes/no - most likely no) no
Is the issue reproducible? (yes/no) yes

Using tweaknews as my server, gives a max of 30 connections. Previous home got a max of 12 mb/s download, sabnzbd would download at an average of 900-1 MB/s. New home has a download of 25mb/s, I'm averaging 750 KB/s. Previously I had 20 connections. At 20 connections I was getting around 500 KB/s, reading around the forums it said to reduce connections to less than 12, tried that, was getting around 250 KB/s. Increasing to 30 has given me the best at 750. What do I need to do to improve these speeds. It sucks knowing my connection is twice as fast but I'm getting less download speeds on sabnzbd.

[sander]

wired or wireless?

[thesuffering]

Wired directly to the modem.

[sander]

different isp?
what speed do you get with Grabit?

[thesuffering]

Yes, different ISPs, was on Frontier, now on Centurylink. Grabit gave me similar speeds to sabnzbd with no configuration changes.

[sander]

If grabit gives the same speed as SABnzbd, it's not a SAB specific problem.

As you changed ISP, it might be your new ISP is throttling your usenet traffic.