I have am a couple months and 6500 miles into having my GX550 Premium Plus. Love most everything about it so far with one exception. When I am at slower speeds (under 35 mph) and slowly accelerate with RPM in the 1500 range, I have a rattle in the cabin. I cannot find the source but don't think it is the door like others have experienced. Not sure if dash or engine/transmission but seems center front area of cabin. Once I get closer to 2000 RPM, it is no more and I don't hear it at higher speeds. Doesn't matter if engine is warm of cold. Has anyone else experienced this and if so, what was the source? Thanks.