SINCE THIS IS UNDER THE VMAX 800 SECTION, I AM ASSUMEING YOU WANT TO KNOW ABOUT PSI TWINS ON A 800. I HAVE TO SAY , I DON,T KNOW IF THERE ARE HUGE GAINS IF ANY HERE. THE STOCK 800 PIPES WERE VERY HARD TO BEAT. POSSIBLEY THE PSI ARE LIGHTER, BUILD HEAT FASTER. 3:16 (yammie tony)