There isnt much done to the carb but even at idle with the idle mixture adjusted for max vacuum using a vacuum gauge it runs rich. I'm running a .018 squirter and I forget what pump cam it is but the accelerator pump is not the problem. The vacuum secondaries open way too soon. I am trying to work that out, for some reason the carb I got did not come with a vacuum check ball or brass restrictor so I am going to try to get one of those to see if it helps keep the secondaries from opening from just 'winging' the throttle with the heaviest (black) spring in for the secondaries. In first and second gear I can take it out to 7000 rpm+ but in third gear I can get maybe 6500 and fourth I can only tach out to around 4500. The power just seems to flatline between 4000 and 5000 in gears above 2nd. And because of the secondaries opening to soon, I get that 2000-3000 bog. The carburetor is Holley's 390cfm 4160 model with a metering block (no jets or power valve). Offenhauser states that with that intake a towing or RV cam with 5000 rpm max should use the 390. A 3/4 to full race cam with 7000 rpm max should use the 465, and a full race cam with 8000 rpm max should use a 500. Holley doesn't make a 500 and more importantly, Offenhauser doesn't say anything about a worked, better breathing head, so I am assuming it should breathe much better than the 465, even the 500. I'm trying to see if anyone had a similar set up or something better than stock with the Offy intake and what carb they used that wasn't the 390, or if it was, what did they do to it to make it run well. I am running an MSD Blaster 2 coil with super conductor wires, NGK racing plugs, and the timing set to 28 degrees advanced at idle. Stock distributor and ignition module.