Brother i do have SE Saloon and faced similar issue, gone through all these road side mechanics, get fuel pump, tank, lines clean...then for injectors and air passage. Plugs were change so no issue with them..The final culprit after visiting Toyota service was the current coils.
Are you facing this RPM Fluctuation once the
a. engine is fully warm
b. On signal its just start increase and decrease for 3,4 times and shut off the engine,
you may see the black smoke during this action. yes at high speeds when gear are engaged from 3, 5th you may not experience..
if above are the issues, just check your current coils they are weak and current is shot with body which i have seen myself. Use Original current coil and this will not be issue any more...