No Flowmasters here, see sig, raced a 01 z the other day fender to fender up to 100 when I guess his speed limiter kicked in and I walked his $ss to 140
As usual can give the driver could make the difference answer. My 99 z 6MT ran a 13.15 stock with practice launching. Stock s197(mine should be in very soon!) 13.4-???. The flows will give you little to no power increase(people replacing axelbacks for sound only, GOOD REASON!). The Z has a 5.7, we have a 4.6, good luck. IMO they will never look as cool! Those LS1s are fast.