something is wrong!?

you are making great power on the top -end , sounds like 600 plus, if the advance spings are to tight it wont advance quick enough, i think if you had 20 degrees at idle with it all in @ 1800 rpm, the motor will be nice and crisp, also if the carb is to fat in the lowr rpm range-that extra timming makes it act like its not rich. leads to quicker 60fts. how flat is your fuel curve ??