Have you closed down the air bypass screw? Also the idle stop screw?

There are two idle speed control circuits in the TB. One is a wax pellet FIDLE valve that is not replaceable and has been known to fail. I know you said you replaced the TB, but with a new or used one? I'd pull the TB and see if after you warm it up some if the secondary fidle valve closes. Use a hair dryer to heat it up.

Not responsible for advice not taken...