Uh Oh... Phil,
That sounds awfully familiar...
That's exactly how mine started out.... Intake gaskets.
I don't think it's relevant how many miles the engine's done... it happens.
And yeah.... It's a PIG of a job!
Hope you had a warranty on it.....
Wish you were a bit closer so I could have hooked it up to my code reader/laptop.
BTW "Easy Start" seems to work better than carb cleaner to test.
I just thought... before you go wasting money (like I did) on Tps's and Iac valves why don't you pop your phone number on a p.m. to me ... I can likely help you figure this out.