Have a 93 LS400 with 131K on it. Looks perfect, runs perfect with one exception. Under load (up steep hills or accelerating at speed.. 70+) the car hickups or stumbles. Have had the car in a Lexus dealer for 3 wks with no cure. Changed out the EC Unit. New plugs. Fuel injection cleaning. New torque converter. I am ready to set it on fire! Has anyone had a similar problem?

 

o2 sensors maybe?

 

Thanks, is there is more than one 02 sensor?

 

theres 2, one up and one downstream.