The bolts have not much to do with power or boost, mostly just max RPM. And turbo ZVH is not known for being a very rev happy engine. On the other hand, for myself, if I didn't use at least new bolts, I would worry and regret each day that I had saved the price of 8 bolts.

As to the con rods, it's RPM, CR and det that also play important role in the con rod killing game. If they are reasonable, then 1.5bar doesn't sound much at all.