The 184 bbk and race head does definitely open these engines up, and if you hadnt ridden a 190 fdx then you would be more than happy with the results. I blew a few ppl out with a 155 race headed hi comp zonger (stock bore, but hi comp piston and big cam with alloy rollers instead of the forged originals) I had, and the 2 184s I have now both run hard enough to scare the pants off unsuspecting riders, but they lose out by 3/4 bike lengths to the 4 valved 190 in straight up drag race. Pretty even in 1st and 2nd, but as soon as I dropped into 3rd I lost a bike length on craigs 190, and by the time we were both topped out in 4th I was three to four lengths behind. Cutting a long story short, if you HAVE to be the quickest, the 190 is the engine you will be wanting. If your satisfied with a damn quick mini, then there is nothing wrong a tb or taki headed 184. Well our zonger 160s are actually only 178cc with the bbk, but whats a couple of cc between friends lol.