I'm new to this board and felt compelled to add my 2 cents. I am the mother of an amazing ds with an IQ of 150. His processing speed is 40 points lower, so naturally I was concerned. I recently spoke with the someone who helped me understand the issue a little more. She compared my son;s mind to that of a ferrari, always working at high performance. She said his processing skills were like having non performance tires on a ferrari. The engine is working at a high capacity, but the tires are holding it back.
Don't worry, this is something that can be improved. It's a matter of working with your child to develop skills that help him slow down a little, learn to think through a process and proceed in a way that works best for him.
We are currently giving our son 3 tasks to complete and no other instructions. He has to map his way through the process. It really seems to be helping.
Hope this was a little helpful.
All the best!