You will see even the slighest hint of ring flutter, in a vacumn trace, especially with a RacePak, because the sample rate is very high. As someone else said, the motor should maintain, or make vacumn during a pass. If it is dropping, or has dips, the motor is NOT happy.
With all 3 kits spraying on our 632, it has 10" when he drops the button and 13" at the stripe.
Think about it, on a nitrous motor, with a gas ported piston, the more cylinder pressure you make, ie, more nitrous, the better the motor should seal. If this is not happeneing, there is a reason. As I mentioned in another thread, about what a plug "should" look like, you will see an unhappy motor MUCH quicker in the vacumn trace, as opposed to watching plugs. Rich, or overtimed, will unseat the rings and even the slighest flutter, will show up in the trace.
Monte