I have an LT8S running on my 3rd gen which has a GT35R single turbo, 550cc primaries and 1600cc secondaries with fuel regulator that is set up at 40psi constant (supplied by a large Bosch fuel pump). Its proving difficult to tune, even though I'm using 99% staging. The Staging is set to occur at 12"Hg / 2250rpm, although I have tried 10"Hg, 6"Hg, 3"Hg etc. I have set WOT as 4"Hg.

The secondaries seem to come in way after 12"Hg though, and the primaries seem to struggle to supply enough fuel to cope with 5"Hg. What I've done to compensate is add more fuel at 10"Hg and 5"Hg. This works OK until the secondaries 'really' come in and flood the engine so that my (Tech Edge) wideband reads <10AFR. But if I take out the fuel at 10"Hg and 5"Hg then the WB is up to 14-15, which I don't like, and the engine gets hot after a few miles when driving between 10"Hg and 0psi.

Also, I notice that if I maintain Load eg. at 15"Hg (primaries only inj) and just increase rpm, my WB reads higher (leaner) AFR's. I am running in Normal mode (not Matrix). Doesn't the ECU increase fuel inj time when RPM increases? Mine seems to do the opposite!

Adrian