I'm having a problem with backfiring under initial throttle. Can anyone tell me what I need to look into?

A buddy of mine helped me tune my 750 HP Street Holley, but it still runs a tad rich with 78/82 jets. I'm totally lost when it comes to engine timing. I'm not sure what what it's set on now and I don't run vacuum. Here's the #3 plug, they need to changed...

Doesn't the black soot mean it's running rich?

http://i46.photobucket.com/albums/f105/zachschevelle/DSC_0001-5.jpg

http://i46.photobucket.com/albums/f105/zachschevelle/DSC_0007-2.jpg

Start by getting your timing set. 16º-20º initial, 36º-38º total would be a good start. 78/82 in a 750 on a 408 street engine seems fat to me. The most common cause of backfire under initial throttle (assuming the timing isn't the problem) is a lean condition. That's usually an issue with squirter size or pump cam profile. Also keep in mind that mashing a dp full open at low rpm it likely to give a lean bog or backfire even if everything else is ok.

Zach, the 750HP Street come with 75F/80R w/ 6.5PV Frt only. Mine runs real clean with this jetting.