can you do a relative compression test, and put in a firing event to see where the spark happens ?

kia do a engine where the crank reluctor moves, and gives the same symptoms you describe .

i chased this fault for ages it gave good vac readings inatialty then went down to 10 in hg .

with a low vac reading the engine will be running very rich, can you create a reading of 18 ing with the mitivac on the sensor to see what the pcm does with the throttle body ??.

not sure how help full this may be but interesting ,

does the scan tool map sensor reading match the mitivac?

if you had any problems with the throttle/ pedal you would have a code for it no?