2005 pontiac G6 engine noise

I have a 2005 pontiac G6 which has a knocking noise as soon as you start the car hot or cold. I have already replace all of the lifters still the same noise. the engine only has 45,000 miles on it and the oil was change every 3000 t0 4000 miles. I also check the flexplate and there was no sign of a crack.
Any help will be greatful Does the knock go away after the engine has ran for a few seconds? If you could record the noise and post it up on youtube or a video hosting site, you can send us the link, so we can hear what you are hearing. No the noise is always there and i dont have a way to record the noise yet i will try to figure it outCar Repair Talk's forum.