LIM gasket needs to be replaced. (lower intake manifold) if kinda a "normal" problem with the 3400. normal that it most certainly will happen. get it fixed ASAP!!!! and dont use GM's replacement its still crap get an aftermarket one. i forget who makes it, but it made better than GM's. gl
use the search option to find out more. theres been millions of posts here on that crappy gasket.
btw, welcome to the site.
