Why get him even more confused? On Holleys/Demons the idle mixture screws are on the sides of the metering blocks. Looks like this Demon has 4 of them. This is the least of his problems.
But yeah, the throttle-base plate is installed backwards on this "rebuilt" carb. Who knows what else is ***-backwards. I think I'd ask for a refund!
Looking at the pictures, I can see quite a few other issues For example, where is the transmission throttle-pressure (kickdown) linkage? Good luck getting it to shift correctly.
