@80 TargaSC
In a nutshell: An ROW (non lambda engine) WUR-089 needs at its vacuum port a higher manifold vacuum to be present so it provides a correct control fuel pressure at normal load/driving.
At high load, means accelerating, the manifold vacuum at the WUR port drops which lets the WUR drop the control pressure as well, so the mixture will be enriched.
Now in your case with a lambda based engine model, as no manifold vacuum hose to the WUR exists, the 089 WUR always sets the control pressure to lower spec and your engine is driving too rich. Additionally ... with your lambda system ..., when engine is cold running or when you accelerate you get an additional enrichment by the ECU!
You see why its one of the worst things driving with a non proper WUR.
I recommend checking your whole system ... follow this workshop and your engine will drive like charm:
https://nineelevenheaven.wordpress.com/the-911-sc-3-0-engine-with-catalyst-and-lambda-control/