Are we talking head bolts, or can I get a more detailed account on what should be replaced? I remember 8.8's might be marked on the head of the bolt but I don't know if my bolts will say 4.8 or who knows what.
I'm talking about the bolts used to fasten the sprocket onto your bike's spokes. The grade of the bolt will be stamped on the top of the bolt. US bolts are indicated by radial lines, whereas the metric system uses a numbering guide. Anything up to 10.9 grade should be made of steel/zinc. 12.9 grade bolts (the black ones) should be hardened steel, and are stronger, but more brittle. Here's a useful webpage:
Bolt Depot - Bolt Grade Markings and Strength Chart
These engines themselves run rather well, it's just the hardware they supply you with is of low grade.