: You really want to consider the ///M Mirrors. I have seen them installed, on of the 850CSi. They look incredibly beatiful.
*** I agree but I heard they make a whistleing noise at higher speeds. ***

: : Also I have some question regarding suspension upgrade. What is the good after market upgrade for 840Ci suspension ?
*** H&R (or Eibach) + Bilsteins shocks ***

When you change the spring coil and shock do you have to replace any related parts ?
*** No, they are bolt-on parts ***

what is swaybar ? Do I need one for my if I am to upgrade mine ?
*** No, not really. A problem is not many available for a fair price. Dinan is very expensive ***

: : I think I got the chassis twist when I go through bumps. What is the my problem ? How do I fix it ? or what can I do ? anyone please help.
*** Check your lower control arm, and upper control arm. They usually last about 60-70k miles. On the upper arm you can replace bushing only (lot cheaper) but on the lower this isn't possible and very expensive (made out of aluminum) You should check your stabilizer bushing but they are last a long time. Make sure the shocks are oke ***