i have a 95 mustang with a vortech v2 supercharger system. i just installed a cheap dragon gauge, and it gets -9 during idle. I drove it yesterday, and i had to almost redline to get the boost to register 3-4 psi. this is suppose to be set up 6-7psi. the sheave on the supercharger looks to be about 3.5" diameter.
Where in OK are you located? Shot in the dark, your kit would be at 6-7 psi at sea level. But some places in OK are around 3500 ft in elevation.
I ran into the same problem here in CO, a smaller pulley on my TVS fixed that problem.