I had reported previously that I found the HTTP proxy filter to cause a slowdown in uploading of files or speed testing. As it turns out the HTTP proxy is fine, the cause is Firefox. There will be minimal loss of throughput due to the action of the filter which I would consider normal. Firefox inherently has a slow file upload. After some research I have resolved the issue. The addition of the following windows registry hex dword value as noted below, followed by a windows restart will correct the slow upload. The actual dword value can be increased or decreased depending on the throughput requirements. The following can be copied to notepad, saved as a reg file, then merged in to the registry. This is applicable to Windows XP/2000, Server 2000, and 2003.
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\AFD\Parameters]
"DefaultSendWindow"=dword:00078000
Hopefulley this information will benefit others.
Jim [:D]