tax exemptation!

I am H1b visa holder and work in a non-profit research institute. I applied the US-China tax exemption policy to exempt my tax and medicare fee etc for the past two years. Recently my I140 was approved and I485 is pending. I wonder if the policy is still applicable to my case in 2006. If I don't pay tax this year, does my I485 will be negatively affected?

Thanks.