98NBM3800

I just got done installing some pacesetter headers on my 3.8 and the car already has a blown head gasket and It happen right after the install not sure why? the car has 75,506 miles and The mods I have right now are K&N cold air intake, flowmaster super 44 axle back exhaust and stock cat and jet performance chip maybe the catalytic converter caused the blown gasket idk but when I have the money I'm getting it repaired but for the meantime what could have caused it? the headers fit fine and where easy install


-thanks robbie