watch my dust - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Also, watch my smoke. See how fast I am, or how quickly I'll succeed. For example, I'm going to turn that investment into my first million, just you watch my dust, or I'll make it, just watch my smoke. The first term alludes to the dust raised by a galloping horse, the second to the smoke generated by an engine. [Colloquial; late 1800s]