Hi,
I am getting the same white smoke symptoms, looks like i have done similar things to you, I have recently also had a new 5th injector fitted and the ECU software updated by lexus - the white smoke isnt as bad as the car warmed up now but the problem is still there. The DPF was replaced about 10000 miles ago so im not sure if it could be this.
Did you get any further on this? I would be interested to know,
Thanks,
J