every .1 you shave off your 60ft is .2 tenths in the 1/4 (general rule of thumb)

a decent 60ft on a street night w/ street tires is 2.0-2.1
drag radials sub 2.0 (1.9's,1.8;s)
slicks 1.7 60 ft or better

so if you ran your 15.3 with a 2.3 60 ft that tells you that your car has more in it..IF you can launch it better that is. your car has a 15 flat in it..just gotta work on finding that sweet spot when you take off

ways to better your 60ft are:

good street tires, drag radials, slicks
higher rear springs to put my weight on the drive wheels
less rotational mass ie lighter wheels, lighter brakes etc.

you need to launch the car at a RPM in which the car can hook with minimal wheel spin, every car at dif mod levels is dif so theres general rule of thumb.

also, you dont want to do a full on burnout on street tires..unlike radials/slicks street tires grip LESS when heated..you just want to blip the throttle to clean the tires of rocks/dirt. you want to stay out of the waterbox as well or you will get terrible 60ft as well.

HV3 insert/ER rockers/3" downpipe/tune and youll be able to hang with a stock GTP hope some of this helps bud