I saw an average of 13 hp from low rpm to redline with the NW manifolds. I've used the cork and stock gaskets and always see better numbers with the cork, don't ask me why, because I don't like them much for durability reasons. With the cork you have to be real careful not to over torque, especially the o ring material on the pedestals. They don't have as much material supporting the intake as the other bolts have. I have a 178 crank pulley. I started with a Code3. The 178 makes slightly more power than the normal sized Code3 style supercharger pulley. My car wasn't responding well to modifications and frustrating the heck out of me until I added the NW downpipes. Don't ask me why because I seem to be in a minority. Just adding a teflon Y pipe and the downpipes I saw 26 hp with them open. 15 hp closed.
As far as times at the track, my best was 12.75 on street tires. My first time out with drag radials I ran 12.14 and that's with no other changes to the car. All my words won't fix what's wrong for you but I hope it gives you useful information. I've bought dyno time after almost every change made to my car so I'm not making noise out my back side. Don't get frustrated and don't give up.

Les