Dropped off the car and we were able to reproduce the thump or clunk under hard acceleration on left turns. They are going to run some scans of the car and also get it up on the rack. Hoping the issue is identified and fixed in short order. I'll keep you guys posted on their findings.
So here's the update guys. Got my car back today and they were able to reproduce the issue with my car and two other IS250 AWD's on the lot. They are unsure of what is causing the clunk/thump underneath the car under moderate to heavy acceleration when making left hand turns from a complete stop. They said they would keep me posted with any updates. 2 hours after I picked up my car I received a call from my SA. He said the head Lexus tech just had received a call from their regional rep in Chicago and he had just reproduced the issue on the car he was driving. The regional rep is escalating this issue for further research. I encourage all of you to try it in your 14 250 AWD's as it is reasonable to assume that this issue is prevalent. If you experience this issue I encourage you to report it to your dealership.
I just visited with Lexus Corporate and they have confirmed that this issue is impacting the IS250 AWD, but at this time they are deeming it a characteristic of the vehicle but are researching the issue to see if a fix will be implemented in the future. I have driven 2 other IS250's at my dealership and they all exhibit this characteristic under heavy acceleration from a dead stop on left turns. I personally think it is a driveshaft clunk. I encourage all of you to step into that accelerator a bit to reproduce and report it to your dealership
I have now experienced the issue and it is fairly consistent. I noticed it on a left turn at an intersection where I had to accelerate quickly to avoid incoming traffic.
You feel the light clunk under your left foot (left foot rest) more so than you hear it. It does feel like the driveshaft if I were to guess. Seems like Lexus is aware of the issue in the US, but not sure in Canada so at my next servicing, I'll bring it up.
I'll also test a right turn abrupt acceleration with a passenger to see if it's there as well.