Guys, I've been shopping for a good price for the GM 3 BAR MAP sensor for a while, and I think I found a reasonable source. Most guys that have it don't have the harness, or expect you to go to Pep Boys, buy a similar harness, and modify it. But this GM dealer in Akron, Ohio had the sensor and harness for ~$81, with 1-1.5' of wires to splice unto:
His name is Dallas (Dal) Slabaugh, 800-362-9494.
sensor part # 12223861
harness part # 15305891