What could cause lumpy ride and uneven idling?

When new, the car had a soft, smooth, ride, almost American. The ride got bumpier. Shocks were gone. Replaced shocks and tyres in the last two months. Ride still feels rough. When idling, engine sometimes gives sudden jerks, like a misfire.

Wife has read (in an on-line manual in Japanese) that this could be connected with bearings, perhaps in transmission. (I can't read Japanese, she can't translate exactly.)

Any help or advice much appreciated.