[tacoma man.]

i beleive that the ect button is for like extra power on take off. it tells about in in your owners manual.
i think it changes the shift patterns. you'll need to read up on it. my truck is a 5 speed so i have never used it. as far as the overdrive use it 45 mph and over. but just cruising around under that with OD on it will just bog down when you accelerate quickly, and may cause train on your clutches, the owners manual has a section on it too.