97 Kenworth t800 with N14 boost pressure

I have a 97 Kenworth t800 with n14 460hp and the boost pressure sensor voltage low was on and replaced the sensor. Now the code is boost pressure incorrect. We put a manual gauge on the intake and are not reading any boost. Truck runs fine. Checked hoses and are good. We pulled a plug on the intake and when ideling there was a vacuum and when at 1500 there was a bit of psi blowing out of the hole. Any suggestions to fix the boost level incorrect code?