[Z-linkCobra]

Need to know the timing. I timing issue could cause a backfire. Also un burnt fuel in the exhaust will cause as well. An exhaust leak will also cause a back fire under de acceleration. Sucks clean oxygen into the exhaust and cause micro explosions in the exhaust. Make sure you don't have any slop in the linkage on your accelerator pump. A little slop goes a long ways to causing a bog. Since you went to a larger squirter and still have a slight bog, that might be your problem or at least part of it.