e30

Not making the right boost. Any ideas on where to start?

I recently tuned and went fbo on my n55 e90. I have currently not making anywhere near full boost and I have no idea why. If anyone could possibly give me some ideas of what could be going on, that would be awesome. It will kind of spike to 14-15 then hold around 11-13 psi. In high gear at low rpm in 5/6 gears there is a spike to 6 psi where it holds.