94 3.8L is like a riding masage car

[trique]

I have a 1994 continental with a 3.8l that is running real rough when just idling, so much it will make the car shake viciously sometimes. When driving, it will go away when accelerating past about 3500rpm's and also on the highway past 65 mph. Accelerating to that point is a rough ride though.

Ran injector cleaners with no help. Has all new exhaust. No engine codes.