Yes cause the 00-01 ECU runs a lil rich and you can use the VAFC for cutting fuel only at WOT only

 

As others have mentioned, you don't need a dyno to measure your A/F ratios - just a wideband sensor, controller and logger.

With similar modifications to yours, my car is too lean for a VAFC to be of much help, with respect to fueling. Here's a plot showing my car as it currently sits and a plot of my car when it was nearly stock. The "B-stock cat back" is the OE cat back with the mufflers chopped off before the "Y".

So, depending on how your upgrades improve flow, you might not be running rich. Mine tune is a little too lean for my liking and I'll be switching to a more capable piggyback in the near future.

 

That's exactly the info I was looking for, thx.

what are you using to datalog?