Settings to Make GT4 run in constant 60FPS? (Settings/Specs included)

[Subzidite]

Specs
AMD FX-8320E 3.2Ghz (might be the reason it was lagging?)
Windforce R9 270X
8GB RAM
Windows 7 Ultimate x64

The issue is my fps is not constant when playing Gran Turismo 4
- sometime it's dropped to 30-45 during car Selection in Arcade and when racing while other AI are surrounding
- and sometime it goes beyond 60 during racing when I'm in front/1st Position (like it was slightly fast forward , didnt press f4)
- most of menus are constant 60

I'll include all of the settings that might required (Emulation Settings , GS , Audio)
I'm not sure if the reason this happen was some of my Config are wrong or my CPU/GPU are too low , or Both

Thanks.

                               

[jesalvein]

if you can overclock to 4.0 Ghz, It'll help quite a bit.
Your CPU barely reaches 1400 STR where GT4 would require a CPU around 1700-1800

4x native may be a bit high too.
Try 2x

[lightningterror]

You should also get the latest git version. Which will give you a fps jump.
http://buildbot.orphis.net/pcsx2/

Also enable HW hacks and tick Fast Texture Invalidation.
That will also give you a minor fps increase.