My 2009 GT that I bought this year had higher than normal vibration at idle while in "D" or "R". I suspected bad engine/transmission mounts, and my suspicions were confirmed with a quick inspection.
The worst ones were the front and rear mounts. The rubber was badly torn on them. I replaced them in September of this year. It made a difference, but the vibrations were not completely eliminated.
This month I replaced the L/H mount first, and most recently the R/H mount. WOW! What a difference! It really smoothed things out after the final one was replaced.
The main reason I spaced things out on the replacement of them was that I had trouble getting them. The front, rear, and L/H ones were ordered from an online dealer website, and they only had the front & rear ones. The L/H one was on "national backorder", with no known date of delivery. At first, I didn't think that I needed to replace the R/H one (it is difficult to inspect while installed.) I later determined that it was also bad, and then I had the same problem trying to get the R/H one. I eventually found both the L/H and R/H ones at a dealer in an adjacent state.
More than one dealer told me that the L/H & R/H mounts were "discontinued" by GM. I don't know for sure if that's true, but if you're experiencing the same vibration symptoms, you may want to try to find the mounts sooner, rather than later.
You can still get aftermarket mounts quite readily, but I've had bad experience with those on another vehicle in the past. They were "OK" in the summertime, but when the weather turned cold, the car would really vibrate. I suspect that they use an inferior rubber compound that didn't have as wide of a temperature range. I ultimately ended up buying the OEM parts to cure that problem. Also, the equivalent Toyota parts may not be difficult to get, but of the ones that I called about, there seemed to be quite a difference in price, compared to the GM part.
Here are the part numbers replaced on my vehicle: (Verify the correct numbers for your particular vehicle)
88975617 - R/H Engine Mount
88975636 - L/H Transmission Mount
88975592 - Front Transmission Mount
88975604 - Rear Transmission Mount