A 2.3 with drag radials @16 PSI isn't cutting it. You'd be doing better with street tires. Remember, ever .1 you drop off your 60' is close to .2 off the 1/4. 16PSI drag radials will slow your MPH down slightly but you're still a little low. You should be 112-114 or so. You need to burn the hell out of those drag radials till they start smoking where you can see it in the side mirrors, then launch the crap out of it. Shifting might be why the MPH is slightly low also. Keep the RPMs up and shift fast of course. Your Z easily has 12's from seeing that timeslip.