1g missfire

[93gtpeater]

So I have my car street tuned. Runs awesome at 23 pounds of boost. Iam running e85, scm 61, bc 272 cams, fmic, 255 walbro, fic 850s, and a 2g maf. Iam still on stock head studs and headgasket. So I cranked the boost up and took it for a spin. It holds at 26 psi but it starts to miss when it hits full boost. Once it goes past 23 psi it will start to miss. I dont know what it could be.