I have a new Low Rider with SE Heavy Breather and FatCat exhaust, with dealer download. My bike pops and backfires through the exhaust when I'm accelerating and upshifting. Usually between 1 and 2, 2 and 3,. It doesn't backfire on decel at all, just burbles a little. But when mildly accelerating, I pull in the clutch and 2 or 3 out of 10 times I get a backfire. My question is....is this normal for a 2 into 1 pipe? A FatCat pipe? Bike seems to run fine other than this, and the plugs look good(light tan). Am I too lean, too rich, normal for this pipe?