I just bought a 2001Harley Fatboy with a Dynajet PCiii (serial). Has a thunderheader 2:1 and a stage 1 AC and the standard dynajet load M805.111. Runs really lean and backfires on decel. Doesn't appear to be exhaust leak, checked it and no air leaking at manifold connections. Any ideas? Do I need a different MAP. Is there something I should but haven't checked? Thanks in advance for any help.