Ls430 Question

[ROSS]

I have a 2003 ls430 with 9,000 miles. I never noticed this before

but now I notice that while driving at highway speeds and lift my

foot of the gas pedal and start to coast, when the RPM's drop

down to 1100 RPM's, it surges up in speed and RPM's to approx.

1300 RPM's. I have started off in both 4th and 3rd gear, and the

same thing happens when RPM's hit 1100, it surges up to 1300 RPM"S

and increases speed. Does this seem like a transmission or ECM problem.