mystery needles in dash

What does the service department at your dealership say it is?

 

I believe KBeck is correct. There is likely an object similar to a toothpick or mechanical pencil lead that is rolling over the horizontal face of the display. As you state the "needle" appears after firm acceleration, I suspect the object is rolling back and forth. The mirror in the instrument cluster translates the motion to up and down. Acceleration causes the object to roll backward, and the image to rise.
Take a small mirror and a strong light, and closely inspect the area directly below the speedometer display.

 

maybe stick a magnet there and try to magneto it out?

 

If it's toothpick or alike it wouldn't work but it is worth to try. Or with the vacuum cleaner with narrow nozzle try to suck it out.
Definitely the idea of PriusInParadise to inspect the mirror with the other mirror and small torch is recommended.

 

should fall under the 3/36, let them replace it, problem solved.

 

I smell a troll.

 

This is not part of the car. The display is a vacuum florescent display it is not capable of displaying black objects.

John (Britprius)

 

All is well!

 

Glad you solved it! I was reading through this thread and getting into a conspiracy theorist, unsolved mystery mentality!

 

Mystery Solved!

Glad it worked out...cheaply and easily.

Thanks for keeping us on our toes. We need a post like this one, once in a while to keep us awake.

 

I bet ya, it's a small sliver of plastic.

(Too Late?)

 

I've just gone back to sleep.

John (Britprius)