Studs it is. My only issue, and one that I had when I pulled the old headers off, is the as mentioned coolant. The header bolts that were in it were super short, and had silicone all over them (the rears had bolts, everything else is studs). The bolts in the TTI kit are a little longer, so hoping that helps. Should I still put some silicone RTV or a thread sealer on, or wait and see if it seals itself? Nothing worse than a coolant leak....