Thank you for the response,
I have replaced fuel pressure regulator, plugs, caps and rotors 4 months ago, it didn't help, also plan to replace motor mount when spring comes.
My idle problem was very erratic when cold, it sometimes can surge +300 rpm, so new motor mount can't help either. From the post in this forum, I feel M119s are very prone to unstable idle. I also plan to replace timing chain, fuel line and fuel filter, will let you know if it helps.
99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.