Okay, I'm back with all new problems! A brief history: I have installed a 2003 F150 Lightning motor into a 1997 Expedition 4X4. Upon start up the first time many months ago it ran like it had cams in it and would not build any vacuum unless revved. I have since taken it back apart from the intake up. Compression test on motor says 165 across the board and the needle on the gauge looked good. Pulled valve cover and verified that it does not have after market cams. Reassembled the top end with all new gaskets and some Indian head gasket shellac. Tested all vacuum lines with air compressor and have verified the vacuum line on the back of the intake is in place. Installed new O2 sensors just in case. Used computer and wire harness from Expedition and had a tune written by Mike at More Power Tuning. Stock pulley's. At this point I am running out of ideas about why, after all that, it runs the exact same way. No change at all. Any thoughts to add to my own would be greatly appreciated, again.
I know we had discussed this some back initially when you completed your build. Just don't know what exactly what was said now.
What are your vacuum readings at idle?? Does it idle rich, lean or unknown?
Ignition timing at idle?? Is it possible your cats are shot building up back pressure?
On to the vacuum lines.....
What do you mean you verified the vacuum on the back of the intake is in place? Are you talking about the lower intake or "turkey pan" 90?
Theoritically this line has a restricter in it and "T"'s off with the pcv valve in the valve cover and upper plenum (rear). This line is strictly for use with the pvc system. I really believe the sole purpose of the turkey pan line is to "purge" oil from the lower intake when boost is present but I am just speculating. I can explain why I believe so if your the least bit interested.
If you happen to be using the pcv lines in addition to breathers you will have a major vacuum leak.
The vacuum lines on the drivers side are also boost reference as they are below the blower. These should be used for the fuel pressure regulator and boost gauge.
I have all other vacuum lines to the vacuum port on the upper plenum (front) This includes the boost bypass valve. The line running to the boost bypass valve runs to the top half of it. I left the bottom line on the boost bypass valve open but it can run to the intake just behind the mass air.
The boost bypass valve should be fully opened with vacuum (throttle closed) and you should be able to confirm if the solenoid is pulling the bypass lever to the full up position. This is critical otherwise the blower will be attempting to make boost while your at closed throttle.
One line from the elbow between the throttle body and mass air sensor runs to the IAC valve. The other to the drivers side valve cover and used for fresh air supply for the pcv system. If you have a breather installed in addition to this line you will have a source of unmetered air entering motor which would make for a tuning nightmare that would be impossible to get correct.
Just a few items you can go through..
Edit: I sent you a PM if you wish to discuss.