So I went drag racing for my first time last night. Went to Darlington Dragway and ran an average of 15.8 with a .4 reaction time. I feel like that's slow for these cars.
i have a 2005 SS with the 4 inch fenderwell intake and a resonator delete

 

It might be a little slow. With mild mods, high 14s are about right. The track, track conditions, humid, etc might work against you sometimes.

Your reaction time should not factor in what it shows for your 1/4 time. The clock starts when you break the beam, so getting a good start is better than getting a quick one if the clock is what your racing

 

What was the DA? High 15s isn't unreasonable if DA was awful.