After waiting two weeks for diagnosis and parts, the lower grille was removed and replaced with a stock grille and the supporting sir deflectors that funnel airflow up past the radiator towards to air intakes. A day after getting the car back the "Service Vehicle Soon" message returned in the DIC and the car was returned to the dealership for attempt #7 to repair...
To recap : 1) new throttle body 2) gas cap and mass air sensor 3) reload updated programming into ECM 4) another new throttle body (supposedly new model) 5) new air intake manifold gaskets and tighten loosened bolts 6) remove aftermarket mesh lower grille and restore original parts due to GM bulletin
Car runs fine, but manual indicates this message indicates engine problem and should be taken to dealer immediately. My concern is the "boy that cried wolf syndrome", someday this message may indicate real problem! Right now it gives the typical air flow codes associated with mass air/throttle body problems and sets at a speed of 40mph, message appears the next time I start up the car.
I've suggested a new computer, maybe there's a problem there. Cadillac insists that cannot be the problem. :banghead
Thank God for warranty, although the last change was out of pocket because they blamed the aftermarket product, though apparently unfounded. :nopity