Cylinder shaker

I purchased a car that past owner used his original tach and converted to for use with the LS3. Problem is it hangs where the last rpm's were on shut down and stays there? When it starts back up it works fine. Any fix for this? A friend bought Autometer guages for his LS3 swap and his does the exact same thing? Sorry if posted in wrong spot (please move if so). Any suggestions would be great! Thanks all....

autocomman

Some just do that, has to do with the type of movement. Tons of 80's chryslers do that too..they needle creepr up to like 2 grand, key on drops to 0. Normal

Cylinder shaker

Thank you! Guess I live with it....