popping noise with nitrous

[93svt]

It used to go to 5900-6000, and the cobra computer is supposed to have a 6000 rpm limiter, so that's what I thought was going on, and it was pretty annoying hitting that quickly with 4.10 gears. I had an A9P and decided to try that, because I have yet to find an lx or gt with an actual limiter, but it already had an A9L in it. I went ahead and swapped it anyways, drove it, and same thing. Turns out I needed better valve springs. I have had the car on a Dynapack chassis dyno, which bolts directly to the axles so there is no slippage, and the tach is not far off. No chip, no extender, just good valve springs and a bigger cam. Ran today with a 75 jet and got a 13.19 on drag radials. Still need to get used to the car and the bottle. Thanks for your replies.