I have black soot building up on my bumper. I assume it carbon, possibly unburned fuel. Mods. to date are hv3. AP605's gapped @ .055, zzp gen3 wires, removed resonator, throttle body spacer, zzp pcm, and I'm sure that's all. I had a 54k mile engine put in about 3k miles ago now this soot **** is building up. Any ideas?

All mods were on previous engine and no issues.