Well WTF is new, I wrote a kick-*** response to your question and then when I went to post it, the f'ing computer told me that I wasn't logged in. Right... whatever. So, it all disappeared! Great. Well, here's the quick and dirty version...
Yeah, it's your MAP sensor. I had the exact same problem. Truck sits and idles fine, but it can't get out of it's own way, and snails move faster. Downright dangerous to drive anywhere it's so slow. You have NO idea how hard it was to figure it out on my stupid truck though, b/c my truck didn't set a code for it, it set over a half dozen codes or so in both my Chrysler PCM and my Cummins ECU (A total of like 14 codes). You are lucky it's telling you that your MAP sensor has a problem!
Anyhow, replace it and clear your codes. You should be golden.
The MAP sensor screws into the side of the engine just below and behind (to the rear of) the fuel filter housing assy. It will require unplugging the weatherpack connector from the sensor, and use a 1-1/4" deep socket to unscrew it.
Last time I checked (that was like 4 years ago), the MAP sensor cost about $150 from the dealer. Not sure if you can get them aftermarket cheaper or not. Cummins parts are such a rip-off.
Let me know if you get it fixed and if I'm right. (I'm 99.9% sure that I am.)
All the best,