Exhaust Torque Values Needed 97 5.7 litre

The nuts that tighten the exhaust manifolds through the DONUT gaskets to the exaust pipes keep getting loose. This time I bought the special nuts from the dealer (not fully hexed, but squared a little) for 3 dollars each.

I want to know the torque values for those 6 nuts. I dont want to buy these overpriced nuts again. I just replaced the donut gaskets, but apparently did it wrong. I got 2 new ones just incase. Any exact procedures for replacing the donut gaskets?

97 suburban, 4WD, 5.7 l

thnaks to all