New engine rebuild 3.1 '97 car install Runs Rich /Rough

Hope someone can help

3.1 v6 lumina 1997 car
please forgive this post, I am relaying for a mechanic.

Also I had a longer post written, but my session expired and i lost all the typing :(

New crate engine installed,

Engine runs, Very rich

check sensors with vantage 2400 5.0 w/KV module.

No Check engine Errors.. (going to check again to see if bulb is burnt out)
Ground straps OK
Fuel pressure OK
crank 24x = OK
crank 7x = OK
TP Sensor = OK <-- replaced with known working unit
Mass AFM = ok <---replaces with known working unit
MAP = ok
spark plugs = ok <--advantage tested with prob
noid lights to harness = OK
cam sensor = Seems ok, but the vantage meter is weird on this one.

I though thesensor is suppose to be +12v on unless it hits the trigger, Then drops to 0v. What it looks like is it is 0v then spike to 12v when the sensor hits....(kinda looks backwards...) not sure about this one. have to check with anolog multimeter. and hand cranking

At first the mechanic thought it was bad injector cylinder 6,
But after we replaced it the sympotoms persist

Other theory is that the cam has 2 sensors on it, (rebuilt with wrong parts..)

I am out of ideas cept pulling all injectors to get them tested..

The mechanic doesnt think it is the ecm relearn, But i heard that their is another ecm relarn that needs to be done..
Crank sensor relearn?

The car runs rich at isle and high RPM, (if even gets to High RPM)

Not sure how someone could rebuild an engine wrong.
Perhaps the mechanic/rebuilder put engine together wrong? Wrong timing? Something else ?

The mechanic is relatively competant, and has put in 50+ crate engines, But not sure how many EFI ones...

Any reccomendation /check would be appriciate,
Should i just take this to a dealership.....

How is fuel pressure, any leak of fuel into the vacuum hose at the press. regulator, any misfire?

Yeah look for a huge vacuum leak or fuel pressure regulator bad, etc.