Stronger headbolts for M104 engine.  Recommended to use with turbo application
 
Tightening instructions:
Tighten bolts in stock numbering order.
First all bolts to 50Nm 
Loosen all bolts
Step one 50Nm
Step two 70Nm
Step three 90Nm 
Let the engine heat to working temperature ~80deg
Let the engine cool down.
Tighten to 125Nm