backfires when down shift

[Palmer72bronco]

My 72 has a bad backfire when i down shift to slow down. sounds like a 12 gauge. Not sure what to do checked for air leaks and retightened headers. But what now any help appreciated. the Engine runs perfectly fine.

[sbolt19]

Man, I remember that problem. I had that happen to me right after I put a set of Cherry Bomb glass packs on, but it ended up being that I was running too rich. I remember a time when I had the doors off and my brother was riding shotgun and we were going down a steep incline and it did that, he thought someone was shooting at us, it was fricking hilarious at the time.

[Palmer72bronco]

just did the timing this weekend at 13 degrees advanced. also it is fuel injected with the howell tbi with a larger fuel pump. it was a freebee that has double pressure of the stock one. i do not know alot about fuel injection but should be burning it but i know runs a little rich at idle. i will check my mileage this week and see if it has gone down. any ideas would be greatly appreciated