I'd recommend using the OE bolts... Not only are they designed to stretch quite a bit (there's a +3/4 turn/270 degree step in there... it's pretty extreme for a tiny 6 mm diameter bolt), but the underside of the bolt head has a curve to it that interfaces with the injector hold down block to better center it for the high forces required to keep the injector in the cylinder head as it sprays 27,000 PSI fuel pressure into an engine that makes 450 PSI compression and thus far higher cylinder pressures than that... all forces fighting against that little 6 mm bolt to prevent the injector from just being ejected from the engine.
So yeah, I definitely recommend the right bolts and using the factory torque spec.