Weak fuel pump?

Here's what I've done.. While waiting for the Carter paump to arrive from Rock Auto i pulled a 3 year old air tec from the 73 Valiant 318 and bolted it on the 273. Hard line port in different orientation along with fuel filter location. Pulled the hard line from the Valiant and installed on the 273 with brand new mopar inline filter that cant be seen through. It is now positioned vertical below the alternator. Replaced rubber fuel line at pump to frame rail and replacd the short one at the tank/sender. New clamps all around.
No difference what so ever.
Installed dual plane intake from Valiant 318 on the 273. Tuned, drove around a bit. I cant exactly say no change in overall performance but the original problem still exists.
Yesterday I rechecked intake torque, installed that new Carter pump. I really hoped to hold back that pump for the Commando build. Oh well, still no change.
I can no longer see fuel comming and going but I'm sure it is. The stumble, and fluxuating rpm at idle, fish bite of a mis unde light throttle/load remains unchanged. Runs right well under load/WOT. Got a match ? LOL