The 3.0 V6 is known to have a rough idle, it tends to get slightly worse as the miles and carbon build up. My wife just commented on a recent trip to Madison, 'is there something wrong with your car it idles rough'. Feels really rough to as she drives a Rx400h hybrid that shuts off at stop lights. The 3.0 may not idle the greatest but it is smooth and happy at higher rpm's.