What could cause poor idle on a 97 Grand Prix 3.8L/NA? I just replaced the intake manifold gaskets (both top and bottom.) The car sputters at idle speeds and up to about 1300 rpm. Sometimes it's hesitant on acceleration because of it. After it gets going, it is fine. Check engine light codes for cylinder misfire and lean fuel levels. I've checked a couple times and I did reconnect all sensors and vaccum lines. I did replace the EGV gasket which looked like it may have been leaking and a vaccum line that had a split connector, but neither helped any. This problem started after I replaced the manifold gaskets.

Optional Information:
1997 Pontiac Grand Prix 3.8L/NA

Already Tried:
Replace possibly leaky egv gasket and vaccum line.