On my 440-6, I removed the power valve and installed a Holley screw-in block off. I had to richen up the jets 3 sizes larger (trial and error) and the engine ran great after I did that! I initially tried several different spec power valves, but they all dumped too much fuel at the wrong time. I was running long tube headers, and a Sig Erson 484/292 hydraulic cam. It doesn't cost much to eliminate the power valve, and the guy at the speed shop laughed at me... saying it was a huge waste of time. (a Chevy guy) Boy, he sure did apologize after I blew the doors off his friend's Camaro! Those were the days when Mopars got no respect (1980's)Right now I am building a 360-6, and I am going to try that same set-up again.