I' ve heard that rod bolts are become a weakness point in 911 engines after 3.0 l since porsche reduce the size from 10 mm to 9 mm in 3.2 / 3.3 Turbo and 3.6 l.
Especially Rod bolts used in 964 models seems to fail if used at rpms above 6700 .
In 993 N/A , 993 TT , 996 TT and 997 TT the rod bolts size is always 9 mm but they were upgrade with a new design and maybe they are stronger for high rpms but i'm not sure and in those models stock rev limiter is always 6750 rpm.
I don't know what kind of rod bolts are used in 996 N/A and 997 N/A that have a stock 7200 rpm rev limiter but i think the size is always 9 mm .
So if revving a 964 engine to 7000/7200 rpm seems to be a sure dead for stock rod bolts ,maybe revving a 993 / 996-997 TT to 7000-7200 is less hazardous and 996/997 N/A models use 7200 rev limiter stock.
Although rod bolts diameter is always 9 mm seems there are difference in strenghtfor each kind of rod bolts.
Do you Know what are this difference ?

 

First picture is 964 rod bolt , second one is 993 TT /996TT/ 997 TT rod bolt