408 tuning with a Wideband sensor

I doubt the 750 metering block has a big enough IFR to stuff .023 wire in it.

Pin gauge the IFR size and if it's larger than about .030 find a piece of wire to reduce the area to the .028-.030 range. that should lean out your cruise a little bit.

The IFR's can be at the top or bottom of the channels.

http://members.tccoa.com/392bird/carbtech.htm