2006 dt466 egr low power low boost

Please read full post before replying! Thank you!

My problem:

1. Lacking power on takeoff/ struggles to get up to speed. Cant get over 45-50
2. Low boost reading low for what it should be according to manual
3. Exhaust back pressure reading weird on scanner. Engine will run noticeably different if unplugged.(check engine light comes on when unplugged)

Parameters:

• Engine: dt466 egr 245hp (not dt466e was after the “e” version and before the maxxforce)
  
• Turbo: Vgt s300 series (fresh overhaul, engine had running issues prior to turbo over haul)(also spins freely)
  
• ICP @ idle: actual~800, scanner~800
  
• ICP @ WOT no load not driving: actual~2800, scanner ~2800
• ICP @ WOT loaded not driving: actual~3500, scanner~3500
  
• ICP @WOT loaded while driving: actual~4000, scanner ~3900
  
• Boost pressure loaded while driving: actual 15 scanner 17-19
  
• Fuel delivery pressure @ idle: actual ~56 scanner 56
  
• EGR: blocked off for diagnosis
  
• Boost leaks: no (pressure checked charge air cooler with piping)
• Exhaust back pressure @ idle: actual~0 scanner ~12
• Exhaust back pressure loaded not driving: actual 25 scanner ~35

Tests completed:

• Tested voltages at EBP connecter all passed
• Tested resistance at EBP connector all passed
• Turbo passes bounce test

Dtc codes: no engine codes. Does have body codes but i think are irrelevant?

Shop manual with specs: Navistar International DT 466 Diagnostic/Troubleshooting Manual (Page 608 of 658) | ManualsLib

need help this is stumping me pretty bad.

Thank you for any help!
-Sam

 

@Flint1
Runs the same with exhaust removed.
Engine is completely overhauled
Grid heater is clean

 

@Flint1
Yes turbo passes bounce test.
just a heads up this is stated in the original post

 

@Inderjit
Tank is pretty clean
On the spec sheet supplied it state’s minimum fuel pressure of 50
Under load it only drops a few psi at most
The vin is
1HTWBAAN07J421227

 

@Flint1
Full out of frame over haul.
As far as being out of time, engine starts and runs to full rpm with no problem.
doesnt fire out of intake or exhaust
Compression is even sounding when cranking
Blow by is at a pretty normal amount

 

@Flint1
Never block cac with a rag when removed.
How would you check if there was restriction?