| Black 'soot' is unburned fuel (high hydrocarbons), which is going to be due to the lack of catalytic converters and possibly a rich tune. You can pull your plugs and inspect, they may indicate you are running a bit rich. What heat range are your plugs, and what base timing are you running?
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1992 300ZX NA 5 Sp (Dead)
1990 300ZX NA Auto 2+2 (Dead)
1990 300ZX TT 5 Sp (Building)
2004 G35 Sport 6MT (DD) |
