I don't want to say to much too quick because I haven't ran or dyno'd them, but these mani's have changed the way my car runs. Before - the build time on boost took a few seconds, now it's instant! Cruising 25mph and stomp down and bam 18.5 and climbing, before it was stomp down and 14.5 then climb gradually to 18.5,19.5 or so. The difference is instant boost, I guess it's the overall added volume?! We will find out on Sunday as I have not even been 2 miles with them yet, I'll report back