Have you disabled DNS Proxy on the N900 ?
Intel centrino 1030 is a basic two antenna single band wifi adapter. 144 mbps would be right when 20MHz channel width is utilised on 2.4GHz wifi band.
On the N900, you may wish to try changing the default channel width from 20MHz to ‘20/40MHz (Auto)’ to see if your environment will permit the wifi card and N900 to operate at upto 300 mbps on 2.4GHz band. You may also wish to read this recent thread on same subject.
