You might want to specify under some certain conditions/mods. My 383 LT4 idling at 950 rpms was only reading ~75 Kpa at idle. The cam is what caused the low readings. Are you talking stock or internal mods?
Stock LT1/4L60E, At idle, what MAP ("Hg) readings are you getting, with a hand held (actron etc) scanner? I realize it's gonna fluctuate some, but interested in getting feedback, on what other folks are reading?