35d Engine Vibration at Idle?

[IndyRon]

Just curious if anyone else is/has noticed an increased engine vibration at idle in their 35d? I now have 9000 miles on it and for the first 5-6k miles, I couldn't tell the engine was running at a stoplight. Now, when I come to a stop, I can feel a slight vibration through the steering wheel and hear a bit of vibration sound coming from the front of the vehicle (engine compartment/dash area). The vehicle runs perfectly with no hiccups, has good power, and otherwise has been perfectly reliable. It seems (or maybe it is just me) that the engine isn't as silky smooth as it was when brand new. Anyone else noticed anything like this? Any documented problems with a vibration being transmitted through engine/transmission mounts or possibly and exhaust heat shield under the car? I had it in to the dealer about 500 miles ago for this, tried to explain it as best I could, and received the car back a day or two later and they stated did not find anything mechanical wrong (didn't state exactly what they did), and that their was no engine fault codes. Just curious as to others opinion. I've recently switched to Shell from Marathon diesel to see if this improves it and I haven't noticed much difference. The vibration is most noticeable when the engine is warm and idling low with the car in gear at a stop. Thanks for the input and suggestions in advance. I otherwise love this vehicle.