The sparkplugs will tell you for sure, but I'll bet that your high speed mixture is way too rich. With wide open exhaust and a freak kit, you will still usually find your optimum jets will be somewhere between 150 and 160.
To give you an idea just how touchy the mixture is, the idle and transition jets come back into play as a 'power enrichment' circuit (to borrow from Carter carb terminology). I gained a bit over 5 MPH at the top end just by readjusting the idle mix for best idle speed instead of rich enough to cancel deceleration popping.
