I have a 1990 ls400 with 89,000 miles on it.Just had a full tuneup done.While driving between the speeds of 40 and 60 or so mph the car seems to sputterd and jerk like the motor is missing or trans is slipping.When I get around 70 or faster it seems to smooth out.I figured it wasn't the motor or it would do it all the time.Any suggestions would be helpful.Haven,t owned the car for about a few months and I'am already to sell it, if I can't figure this out.Thanks.