97 Camry Stalls at Idle

97 Camry, 130K miles,

intermittently (about 1 in 5 or 10) stalls when rpm below 1000. After stalling, initially won’t start. After about 30 seconds waiting, can re-start. No engine lights on. Otherwise runs well, except ? occasional hiccup. Two shops couldn’t figure out. Had “induction service” didn’t fix. One shop found “ghost code” P1210 (“injector control pressure above expected level” per my google search).

Would appreciate thoughts about next diagnostic steps (to pass along to a repair shop). Thank you!