Thanks to all of you, especially dbextreme for narrowing down the problem exactly.
Got the new MAP installed and after figuring out that the other MAP is used for a baro-sensor, the car started, choked for a second, then fired right up into an excellent idle. Everything seems back to normal, but I'm of course worried that I damaged something in the process. Idle seems great, car heats up, no funny smells - I think we're good to go.
Thanks again, guys.