rx7s i thought used air pumps
getting a highflow cat won't make it quieter.. i tried a catco with a fs 4-1 and aem exhaust.. no go.. only thing that would make it quiet was ditching the race header
edit.. whatever you do, don't toss your stock cat.. i'm still not convinced some of these highflow units would pass visual inspection or sniffer without some 'help'.. but i could be wrong..
getting a highflow cat won't make it quieter.. i tried a catco with a fs 4-1 and aem exhaust.. no go.. only thing that would make it quiet was ditching the race header
edit.. whatever you do, don't toss your stock cat.. i'm still not convinced some of these highflow units would pass visual inspection or sniffer without some 'help'.. but i could be wrong..