I have a 2006 Silverado 4.8 138,000 miles, about a month ago I had new exhaust manifold gaskets and all new hardware to get rid of an exhaust leak from 2 broken bolts on each side, fast forward to after the repair I’m still having exhaust fumes coming through the AC without recirculate on and while at idle. Any ideas on what to look at next?

 

Sound's like you still have an exhaust leak. Check for signs of black soot around your new gaskets. You may have a warped manifold hints the broken bolts.