For Stg2 shouldn't there be a catless Uppipe?
Also what size piping on the Exhaust parts you installed?
What was the weather conditions while on the dyno?
Are you sure the dyno was in 4wd and not 2wd? (I've seen that mistake)
Which type of dyno, Mustang or Dynojet?
What gear did they test in?
Has the car been well maintained, such as new/clean fluids?
Do you have different size wheels, If so was that taken into consideration?
How about you give us more to work with