Previously I had the police interceptor manifold that came with the current 428 that I purchased from Steve P. who is riding along with Jay this year. It had been port matched. Before that I ran a HM medium riser 1-4v on my other 428. At this point there really isn't much different performance wise, car runs about the same, but I haven't had a chance to fine tune the carbs yet, although I wouldn't expect large gains. My opinion is at my relatively mild horsepower level I'm not taking advantage of the potential the medium riser 2-4v manifold has. If I had another 100 HP there'd probably start to show a difference. That pretty much agrees with what Jay found dyno testing intakes for the book, the good ones made similar power ( at my level ) it's the bad intakes you need to avoid.