I personally have seen a FC with a Cosmo 13B-REW rev to 15,000 on 2 pc 2mm Atkins seals. He did it 2x by mistake but they held, car was tuned for 12,000 rpm, The motor was used over a year with 2 different turbos (TDO6 25G SH, and a T51s) This was mainly raced on the street and track, not exactly a daily driver mind you, half bridge engine as well. So as far as what they can rev too, its all in the tuning