Dodge Avenger MAP

My Grandson has a '98 Dodge Avenger 2.5L. He removed the intake plenum to replace valve cover gaskets. When he got it back together it had a 1297 MAP sensor code. He did not replace the plenum gasket. He replaced the MAP sensor still has the 1297 code. Idles erratically, dies when you take your foot off the gas. Plenum gasket vacuum leak?

low vacuum. probably gasket, make sure all lines are hooked up. low vacuum will cause map sensor to read wrong.