Confused on 1/4 mile speed loss

Hey I installed a BBK twin 65mm throttle body on my 03 Cobra and the throttle response was alot better and the sotp feels like I made power but I went to the tack and ran a 12.6 at 109mph . Last time out before the throttle I went 12.5 at 115mph. How could I loose 6mph in the 1/4 mile. That seems like alot. The best the car has ever done was a 12.2 at 114mph. I'm realy confused, could I have lost power, do i need a tune or what.

Its not so much that I was looking for a performance increase my concern is that when you hit a ET thats .1 off and loose 6mph in trap speed tells me I might have lost some horsepower but my reaction time and 60 foot still cut a close ET. Like I said I've run a 12.5 at 115 mph so a 12.6 at 109 doesnt seem right. The conditions were 70 degrees and partly cloudy and the tire pressure was the same as the last time I raced it, its not a daily driver. Do you think my tune is off?????? Also I plan on getting ported and running 14psi soon so th eTB will be better used. By the way anyone want to buy a 75-125 ZEX dry kit with window switches included?? Let me know and make an offer. THanks for the input guys