You can test it on a bench if you've got a spare wiring harness, but not so easily on the car. If your mapping guy can get hold of an EPROM emulator it's very easy to see if the MAP sensor is working, as the ECU will trace across different load sites as the MAP value changes.
You could open up the ECU, plug it back in to the wiring loom and turn the ignition on (but don't start the car). Then with a multimeter you can read the output voltage of the MAP sensor and check it's sensible - you're looking for circa 2V with a 250kPa sensor at atmospheric pressure. Be bloody careful if you do this, as you're exposing the PCB - so you need to keep it away from anything metal so you don't short stuff out. If you're not sure, don't do it!
I replied to your email from the weekend BTW. You need to check what your ignition timing and CO pot are set to. If your mapping guy changed these from stock to get the car back from the aborted mapping session, they could be way out.