Let's get rid of Pango support first. This is easily done by editing your .bashrc file and adding at the end
Resource your .bashrc with
$ source .bashrc
Short of recompiling Firefox (which appears to be a daunting task), we have found something that helps if you have RAM available. The trick is to keep the disk cache in /dev/shm, a POSIX-compliant temporary filesystem (tmpfs).
Let's use /dev/shm to help the entire system as well, so modify /etc/fstab as follows (see above link for what the defaults values actually are):
/dev/shm /tmp tmpfs defaults,mode=1777 0 0
Now, using about:config in Firefox, set the value of browser.cache.disk.parent_directory
to /tmp. Firefox will automatically create a /Cache directory there when it runs. You can see it working with df -h.
BTW, Firefox will not use tmpfs when you are in Private Browsing. Then, Firefox disables the disk cache, clears the memory cache and uses memory cache only.
Using /dev/shm on /tmp may also offer advantages to systems with multiple CPUs.
I've also seen a script that moves all of ~/.mozilla to tmpfs and
There's some talk of win32 Firefox on WINE being faster than native Linux.
You can also mount ~/tmp the same way with:
/dev/shm /home/USER/tmp tmpfs defaults,mode=40700 0 0
If you want to know how your build of Firefox was done, check its build configuration with about:buildconfig.