Since I can't post to your thread here's some thoughts. Before you go throwing parts at it run another DM and post it.
Also does the check engine light come on? Ever?
You may have already done these things (I can't see your post while writing this.) but does the throttle pedal actually open the throttle all the way. Takes two people to check.
Since you said the turbo is free and that you've cleaned the air filter can you power brake it and make boost? You should be able to mash the brakes and rev the engine all the way to converter stall and have it then push through the brakes.
You might try driving it without the air cleaner and ducting, just to confirm that there is not a restriction somewhere.
With DM running and the motor off log throttle position and/or voltage while slowly pressing the throttle to the floor. It should rise smoothly from about .5 volts to about 4.5.
Listen to and feel the exhaust. Does it sound free and open?