My Toyota Avalon run fine when cold then bogs and wants to stall when warm why?

Try cleaning the idle air control valve. It has 2 coolant hoses and 1 vacuum type hose attached at the bottom of the valve. I assume you have the v6 1mzfe engine, but the 4 cylinder IACV cleaning is same. The valve changes relative position as the engine coolant warms the valve. As the engine warms up, the rpms normally gradually go down from the cold start rpm, because the valve closes more as the warmer coolant pashe's through the mount body of the iacv. My idle was high after warm up because the valve was sticking. I suspect yours could be sticking in the opposite direction. There is an electrical connector on it that gets a voltage input to vary the valve position. It is basically a frame for an electro magnet with a grey connector housing molded on it. Disconnect air box and maf sensor plug and remove 2 vacuum hoses Loosen 2 clamps and Remove air duct/maf sensor from throttle body section . Disconnect center IACV hose (vacuum) Mark position of grey connector body, remove 2 screws, and remove magnet coil/plug from IACV. Rotate inner IACV spool/cam back and forth while spraying throttle body cleaner into the pick up hole located in front of the throttle body burrerfly disk inside the air box side of the intake. The spool is spring loaded, so slight resistance while turning it cw is normal. I used a full can and a half on mine before it was fully cleaned. I cleaned it twice due to a minor improvement on the first try. If the screws are stuck, good luck. A new IACV is about 190 bucks... I hope this helps.