Thanks for the advice.
I will change the cap, rotor, plugs and wires and do the other maint. procedures you both mention. I do and always have used 91 octane. I have cleaned the injectors.
Thank you for taking the time to respond.
My 93 GS 300 hesitates until it is fully warm. It is dangerous to merge into traffic.
This does not happen during the first start up of the day...only after it has stopped and partially cooled down.
One Lexus mechanic said that the "Air Flow Meter" might be the problem...so I bought a used AFM and had the same problem.
Thanks for the input.