i do agree with u rody. the sirio carb is not reliable. only suitable 4 big track. what i'm trying to say is, once i bought the v12, i expect there's something new inside it compared to x12. at my place the v12 is much expensive compare to the rest(non mod engine). whta i did to my v12 is 'port n polish'. then only i feel the power of RB. my previous engine was RB Rody Roem. i love the engine especially the top end.. thanx 4 ur explaination.