When you removed/cleaned/replaced the throttle body did you do any of the following:
In no particular order...
1. Replace the gasket between the TB and inlet manifold?
2. Replace the associated vacuum and breather hoses?
3. Clean through the breathers from the sump to the throttle body?
4. Clean ALL the orifices in the throttle body, including the 1mm one and not just the main breather one?
If the answer to any of these is no, start there 
1. The gasket was replaced.
2. Only one hose has been replaced, a few years ago, the rest seems fine.
3. If that is the black pipe with a 90-degreee hose on top, then yes it was cleaned last year.
4. I cleaned the throttle body and all the associated hoses quite carefully two times last year, and replaced the gasket the second time. I never noticed any difference however.
As I didn't really know what to do I just replaced the whole throttle body and gasket (again), with brand new parts. After that everything just went way worse. Now it is somewhat hard to start, and the orange light goes on right from the start. Then it has audible erratic idle and jittery/stuttering RPMs when driving. Sometimes the throttle just stops responding completely. This can't possibly be related to throttle body now? Fuel issue?
(yes, I waited nearly a minute before first start)
What is the small round part that is connected to the throttle body by a very thin pipe? is that something that needs attention?

(not my photo)