It leans out the A/F a lot from what I understand, I assume that is why WR sells a "fuel computer" with the manifold as well.
I know for a fact it runs dangerously lean without that E-manage in it.
Basically when I was down in Van, after they test drove the car with the wideband on it Ben confirmed that without a tune the manifold was making the car run way leaner than it should. He said I was actually losing a lot of power as a result.
He tuned the car for the manifold and all of the other parts that were on it that time. The only power part I have added since has been the UR pulley's which shouldn't really have any kind of affect on it.
I will bring the software by and you can have a look at the tune on your laptop... also has cool real time graphing which is neat
If Justin has that test pipe with the wideband built in still we could theoretically install it, hook it into the Greddy port and tune the car that way. Not exactly something we can do on a Sunday, though it might be a cheaper option just to buy it from him than trying to dyno tune it.