hi aF Tim
that will be your problem, everthing that you have described is down to the lexus, ( dont waste your time going to lexus they will never work it out), do a leak off test, change the injectors that are faulty.
If you can get injectors from a 2008 car onwards, as denso changed them in 2007, ( I wonder why???)
changing the injectors is easy, just make sure the engine is warm when you pull them
good luck.
ps then sell the car, the is220d is the worst car that lexus made in my opinion