I have a f250 with alot of performance mods. The turbo is a non vgt. There's no waste gate or bov to be found. When I spool it up and release throttle, I can hear what sounds like the typical bov sound but can't figure out where it's coming from. The reason for searching is it will not build over 28psi. When it gets to 28psi I can hear it releasing the excess pressure so something has to be adjusted to only go up to 28psi. Any suggestions?