Any header will leak if you dont tighten it right, that's first. You tighten them from the center bolts outward, and use good gaskets. I wouldnt loktite them personally, torqing them properly usually does fine if you do it right and put enough grunt into it (torq them to spec) you'll have more trouble trying to make sure the y-pipe seals to the headers.

 

I thought Macs don't have a CARB number. Jet Hot LT's don't either but they do have hookups for emissions. You just won't pass the visual.

 

I checked into that and macs don't have carb #. so, they're not smog legal. SLP do have carb #. Lt's relocate cat so they are out , too.