I am a Chinese working for a US company in China. My boss sent me to US participating a R&D project for 10 months in 2006 with L-1 visa and I finished my business trip to go back China at the end of 2006. I research US tax law. It seems I need file Dual-Status return in 2006 because I stayed in US more than 183 days for my business trip. However, there is tax treaty between China-US. My friend told me by treaty tie-breaker, I can still fill 1040NR instead of Dual-Status. Is he right?:)

Probably, because you have maintained a closer connection to China than to the U.S.