Will An In-Line Fuel Pump Help?

[1989GT]

I don't think the 30# injectors are maxed out. 350 rwhp with a 15% drivetrain loss would be about 411 bhp. 30(8)=240#'s of fuel/hr. Should be more than enough to support that. Also the 255lph should support over 500 rwhp. Now maybe the lines aren't up to the task for the nitrous shot, I could see that, but there's no reason for you to be running lean when on motor. Obviously your tuner pulled fuel, when tuning the car, and I think by bumping up the pressure you're temporarily tricking the computer to add more fuel. But as soon as you drive the car for a little bit the computer will "learn" and pull the fuel back out and you'll be back to square one. I say go get it retuned, and look to upgrade your fuel lines if you want to be safe about the nitrous shot.