2007 Trailblazer LS Idle/Stalling Issue

[glock19c2004]

07 TB has been a good vehicle so far, rolled 100k on it and its been down hill since. :-)

Few months ago it started having issues when coming to a stop, the RPMS would severely fluctuate and lights would dim and brighten, defrost fan would rev up and down as well, but once stopped it would level off and usually idle fine. Then it started dying completely when braking and/or slowing and turning. I had the throttle body cleaned and ran injector cleaner and system cleaners through it. Didn't have a noticeable change with it though, also replaced the battery which was tested and found to be bad, but still had the RPM/dying issues.

A couple of weeks ago drove it to work, parked it and couple hours later went to leave for lunch and it was completely dead. Jumped it and it started fine, ran as it had been running. Then last week it died and and wouldn't charge back up. Jumping it would get it started right away but as soon as you stopped it was dying and needing jumped again. Got in to the dealer, diagnosed as a bad alternator and charger pulley. Replaced those and still had the same RPM and dying issue as I was leaving the dealer. Turned it around and dropped it right back off to them. That was last night, haven't gotten the call yet as to the new diagnosis, but wondering if perhaps someone on here has seen it before and have any ideas?

2007 TB LS 4WD 4.2L 103k miles

[glock19c2004]

UPDATE:

Dealer pulled the throttle body off and thoroughly cleaned it all out and then performed the idle reset which I am fairly certain previous mechanic did not do when I had it cleaned a few months ago. Got the TB back yesterday and drove it all over last night and to work this morning. I don't believe it has run this well in 3-4 years. Also got 2 small recall repairs completed as well that fixed the one headlamp being out issue and coated the door panel switches. Nice to have it back for the cold, slick weather we are getting.