disapionted with dyno numbers

[302crew]

ookay i took my car to the dyno today these are my mods 302 bottom end edelbrock heads 6037's milled down 50 thousands of an inch rpm air gap intake demon 650 carb custum cut cam lontubes 373 gears and the track without any tunning i was able to go 12.3 @108 i took it to get tunned and they siad i have 285 rwhp @ 5750which seemed kinda low it had 296 pounds of torque @2500 then i sprayed it with my 150 shot direct port kit this is where i really got upset it only went up to 338.4 rwhp @5250 and the torque went to 417 @3750 does anyone have any suggestions on why that only increased about 50 rwhp im kinda pissed i dont know if the dyno is being operated right the car kept spinning the tires and even one time the clutch spun which i wasnt very happy about because i cant even get it to spin on slicks o yeah its a mustang dyno are they better or worse than a dyno jet if anyone has any advice please let me know