Roush 427r only made 400whp :(

[Ace23]

Let me add a little Mayhem to the mix. Just got off the chassis dyno my car has a Keith Craft 427 with a motor dyno sheet showing 589hp give or take a few hp. Car went from a Holley 770 street avenger to a Quickfuel750......on the Mustang dyno it made 375rwhp and I will have to get the torque number as I have already forgotten. Pretty disappointing but if it runs better thats all that matters. We even did a compression test as the tuner was a bit alarmed and felt like the car should have been in the 420hp range on his dyno as other 427's have been......and before anyone ask the airfilter was taken off and that only made a 4hp increase. The sidepipes are not stock SPF pipes they are the Firefly brand with 2.5" diameter.