Sir, I worked on that particular 1KR-FE that I mentioned before for vibration issue. Not knocking
Like i said before, the idle is factory set very low. There is one jugaar suggested by a mechanic to insert a padding in the accelerator sensor that raises rpm in IDLE. I find it to be a dangerous solution as padding can get stuck anywhere and would pose problem.
Furthermore, the vibrations were increasing becuase the Idle Air Control (Not IACV) was not responding quickly to electrical load of lights. It would allow the rpm to drop till 600 range under certain conditions. Although it would pre-judge the AC on button and would raise rpm before clutch engagement, it would respond slow to either electrical load or putting the car in D.
Regarding knocking, you should check what fuel you friend is using. I am not talking about high octane. Which brand actually?? Has he ever replaced plugs with so called PERFORMANCE upgrades?? What's the gap set at??
We can plot the knock retard parameter to see under what conditions the car is problematic??
You'll have to excuse me as I am less knowledgeable about Toyota's (for now )