If your car is basically a stage 2 Star except with a 6:1 disc then you will need the 12:1 FMU disc. That is what stage 2 Star kits normally ship with. Without it and still using the stock FPR and stock injectors you will not get enough fuel under boost. That is why you are hitting 1600*. Say if you have stock FP of 52psi ... with a 12:1 disc at 6 psi or boost you should be seeing ~124psi of fuel which is the safe range by far ... with your 6:1 disc at 6psi of boost you will be seeing ~88psi fuel. That isn't nearly enough fuel.

Even if you are working on the 8-injector setup get a new disc for the vortech FMU. You don't want to risk melting anything by running so lean.

-"Easy Mac"
05 Mazda RX-8 (RR8 #88)
99 Eclipse RS 398whp & 372lb-ft