You lost about 30-40HP somewhere to drop 4mph.
When I got my car back together with the Canfield heads I went to the track and ran a best of 13.65 @98.6mph. I was really pissed the car ran great no missing or nothing.
I parked the car for two weeks. I had decided to remove and sell the crappy Canfield heads and put my ported stockers back on cause it was faster with them.
I removed my throttle body and guess what, the #4 injector was unplugged.
I went back to the track and ran high 12's @105-107mph.
Hopefully its something you are overlooking.
You need some dyno time. I sometimes use my G-tech as a tuning tool.