This is what I got fellas. Mods in my Sig. MTI put her together and when we sprayed the 150 shot just for the hit I got good numbers. I took it and dyno`d her at G-Force and we seen it got alittle lean so I added a 255 Walbro in-tank with my T-rex fuel pump and 30lb injectors. Now she is doing fine. What I`ve got is a big dip in power up high. She hits like a mother and when I get into 3rd Auto she takes a nose dive and then tries to come back. I took her to the track last night and first run I got 6.92 and she fell down hard right before I got to the end. I felt a easy 6.75-6.8 was there. I ran 3 more times and she did the same thing at the same time. I got 7.0`s all night. She did this on the dyno also and A/F was good. I`ve got everything in sig and shes built good. I don`t know whats happing, but I ran 7.2`s with my old X1 cam, 100 shot and LS6 intake with Ported TB stock MAF with FLP`s. Somethings not cooking right!! Has anyone else had this problem? Tell me what you think fellas. I need Help, with the power I got- I felt 6.7 should be a norm all night long!! I even tried N/A and I ran the same as my old set-up 7.7!! What the Heck!

 

Sounds like you might not have enough fuel pressure at higher RPMs and the FPSS is shutting the nitrous off. Have you tried using a direct pressure reading gauge plumbed to the end of the fuel rail and see what the pressure does? You might need bigger injectors.

 

I`ve got fast fuel rails ordered and a set of 42lb injectors. I was going to just put the rails on, and use the injectors with my 408 build next year. I guess I need the injectors also now. What do you think? Anyone else?

 

The rails and the injectors won't hurt anything but if you were wanting to save them for the 408 try reading the pressure directly, F/P gauges are cheap.

 

I have a gauge on my pillar for fuel and Nitrous psi. I haven`t seen a drop in pressure. But I can easly miss it racing on the track!!

Come on guys, any help!!