missing and hard starting after replacing head gaskets.

What is your question?

After replacing head gaskets on 3.5L H.O. it will misfire backfire and start hard . I changed plugs (one had bent electrode )to no avail before I put it together I cleaned throttle body but did not spray cleaner directly into the throttle body I also double checked timing. when I throttle it I hear a lot of air is this normal?