Not exactly true. It depends a lot on the CPU you are using with the chipset.
The G31/G41 is an economy chipset with a limited FSB frequency range. Used with a CPU with up to a 200 MHz FSB, it's pretty good.
Your problem is the P4. P4's simply do not have the overclocking headroom that the Core2 CPU's do. Here's what you can try:
Shadow's Gigabyte motherboard OC guide:http://www.tomshardware.co.uk/forum/page-245679_11_0.html
It's for an EP35-DS3L but all the Gigabyte Core2 BIOS's are similar. The G31 will have fewer adjustable settings.
Take the memory settings off Auto and set the System Memory Multiplier to 2.0.
Now, start pushing the FSB freq upward. You need to constantly monitor your core temps.
If you are running stock cooling, I doubt if you can get much past 3.2 GHz.