Hum,
on dial up my 1.0.4 firefox downloads the page in less than 3 sec...with the hacks....but it’s on an xp machine...
Sounds like the linux implementations of the browser doesn’t like those hacks.
Or you have a corrupt install of the browser.
I would do a clean install just to make sure.
(imho, even without the tweaks, it’s safer with firefox)