It will defuel sooner. The actual air volume would be less than the perceived, so it would "think" it has too much air for the fuel/power output. EGR position would not likely be effected much, if any, but could go nuts 'cuz the output doesn't match the input. It's a delicate balance, and if you lie to it w/o computer intervention, it'll throw a fit (SES, limp, etc.).
Bad idea.