Went to Byron Dragstrip and ?????

I have a 1990 GT Mustang. I am in college and I work on a tight budget but basically I wanted to have a car that would run with the new Z06. I started off with an old rusty block from a 1984 GT and I built it up to this beast! This is what I built and installed in my stang. I worked my @$$ off at Pizza Hut for 2 years and here is what I have:

Balanced and Blueprinted 331 CI, DSS internals 9.5 c/r, AFR 185's, Trick Flow Track Heat Intake, Trick Flow Stage II camshaft, 75 mm T.B., 80 mm C&L mass air, 30lb injectors, Scorpion 1.6 RR, BBK 1 3/4 long tubes, O/R H-Pipe, Flowmaster 2 chamber w/ dumps, 4.10 gear, Tremec 3550, Spec Stage 3 clutch, UPR blue thunder shifter.
I had a bad experience balding BFG dragradials within 3 weeks of buying them and i figured i was gonna get some Kuhmos. I knew they would spin like hell but they might last longer! I figured i would spin like crazy, they weren't that bad though. The track was real sticky!

I went to Byron Dragstrip this past weekend and ran the car for the first time. I knew I would be dissappointed so I prepared for the worst so...my first run with a .016 R/T!! and 2.104 60ft!! I ran a horrible 13.9 @ 103.4 I thought I would do bad but not THAT bad! 103!!! WTF?? This combo I thought was good for about 425 hp! I thought preparing for the worst meant trapping at like 107 but 103? How am I missing over 100 horsepower? I immediately popped my cobra RR hood and cranked the distributor clockwise til I couldn't spin it any farther...the plug hit the water outlet. I dont know how many degrees this was but it sure helped!! My next run netted a 13.5 @ 108 with a 2.2 60 footer. I got about 6 runs in totally and the best I could get out of her was a 13.449@ 109.07. This is w/o letting it cool down because I had an hour to complete these 6 runs. (i got there late) I know the E.T. could be quicker because the Kuhmo 245/50/16's were chirping into 4th! but the MPH is my question. Remember from up above that my goal was ZO6 area which I figure is about a 12.5 @ 115 or more. Where in the hell am I missing the other 6 mph???? that is either 60 hp or 600 lbs.! I dont think my car is THAT much heavier than a ZO6 so what gives?? If I could get any suggestions, that would be great. I just want to make sure that I am not crazy. I know my car has more balls locked up somewhere inside! And no, it isn't missing. Its running on all 8.

Thanks for your help guys. I am broke right now and I can't afford to do much else to this car. I guess I will be stuck with what I have til I get out of college and get that 2006 Cobra!