Leak at 1700rpm

If it was missing any bolts or if any were loose before the repair was made or if the gasget was not changed when the bolts where replaced "chances are its still leaking. Check it again but at night in the dark try to re produce that same sound. Somtimes you can see flashes of flames coming from that area also make sure all your plugs are tight one or more might have come loose[or out] the manifold might be warped or cracked and somtimes a blown head gasget can make that sound good luck'' hope this helps"