what happen with my NOS?

[5000cc]

Guys,last night i went to the track to tried out my new NOS 75 dry shot.Before i put NOS i ran the best time of 14.45 with edelbrock intake,72 proM,24 lbs injectors,fully exhaust,aluminum drive shaft,traction bar,pullies and stock 16 inch pony rims with not-so-much-of-treads-left tires bad clutch and bad synchro.Last night i ran 14.46 with the juich off the line with cobra upgrade tranny and new king cobra clutch,new 15 inch weld rims.traction was a problem but not as bad.I tried both idle off the line and play with rpm off the line the result still the same.After 3 runs i experience detonation on 3rd and 4th gear.I have stock plugs with 0.054 gap,retard timing to 8 degree,stock fuel pump and fuel pressure is 47 psi with vac.line off. What the hell is happen here!I thought i would be running low 13 or even high 12. What have i done so wrong? 93 coupe.