Avensis 1.8 valvematic, lack in power

[Sshab2011]

Hi guys has anyone come across issues with lack of power on avensis 1.8 valvematic 2012 plate, 

Problem is its showing lack of power, it asks for extra revs when taking off, when approaching a junction and put into neutral it seems as if the car is about to stall revs drop down to 500 and jump back up above 1300rpm and then gets stable again, I've had a look at o2 sensors, maf, air leaks, spark plugs, cleaned throttle body with carb cleaner, changed purge valve, it's driving me nuts. I've also done idle relearn on it, but no joy, if anyone can give me a solution I promise I owe you. 

Most appreciated