What is the best tire pressure for sedan with stock sports spring...i felt that it is too bumpy, can i acutally reduce the bumpyness by lower tire pressure?

 

Dont know the best pressure. I keep mine around 32-33 lbs.
I have the stock suspension. No bumpy ride here.

2003 TwBlue 5AT Sedan, sunroof,
Graphite Leather, splashguards, HKS exhaust,
14 wire Grounding kit, 350Z duct, Stillen CAI
Underbody rear diffusers, Drilled alum pedals

 

The manufacturer's recommended tire pressure (according to the label in the driver's door) is a mere 30psi. You can try it. I usually run 35. It helps a little, but not much, as the tires already have a fairly low profile.