How much boost are you running with factory headbolts/gasket

[SuperTurboD24T]

Head studs are a must, and if you can do it, install the factory metal gasket. It is proven to not leak at manifold pressures of 2.5 Bar and above.

Without those two details, you could be ok with the stock turbo and ~25 psi, provided the stock head gasket is in good shape. The only problem is how do you really know if it is solid. The same would go for the head bolts.

I might suggest you get studs at a minimum, since they are very easy to install, and do not require you to remove much of anything compared to a head gasket install. Just replace them one at a time, making sure there is very little to no oil in the block threads.