I have a Carter performance 625 on the back as my primary and a 1406 on the front. I have the same metering rods Jets and springs in both. I have 92 jets in the secondaries and 95 in the front with 7547 metering rods. I have the medium Springs #3. I have a wideband O2 sensor in the driver side exhaust. I did two adjustments as always LOL and put the 7547 metering rods in in lieu of the 7147's and brought the idle almost up to the 14-7 I would like it to be. But at the same time I put the number 4 heavier Springs in and it made the secondaries go away lean and lose power. I put the number three Springs back in and everything kind of went back to normal with the idle again at 14 5 or so and at cruise speed it was around 13 2 to 13 7 but again wot was down to about 11 2 to 10 9. At this point I'm thinking getting the 89 jets for the secondaries and trying to get that wide open throttle up to a 12 5 where I want it. Also I have all the vacuum capabilities plugged all the way around the carburetors and I'm just wondering if these economy carburetors would rather have the rear vacuum ports going into a PCV valve and getting a little more air? On the passenger side I run an Evac out of that exhaust and an open breather on the driver side. Anyone's thoughts and experiences would sure be appreciated as this year I want to get these carburetors exactly the way they should be.. Thank you..