Why does my vehicle bog down when I floor it?

SUV would bog down when I floored it, everyone said it was the catalytic converter was clogged. so, I cut my catalytic converters off and straight piped it with three-inch glass packs. but when I floor it, it still bogs down sometimes. What else would it be? But soon as you let off the gas just a little bit to where it's not on the floor it goes like it has all power, but I just can't floor it unless I'm already doing bout 80 then floor it then no problem!! It will even backfire sometimes, but it doesn't do it as bad now since I cut the converters off. Also, when I first start it if I don't turn the traction control off it will drive normal for a few minutes then boom no power or nothing. I can floor it or whatever no engine power period until I turn the traction control off then no problems.