OK heres the deal I have a 95 GSR stock except nuesspeed header which has a slight crack in it if that applies to anything with this and I have a cheap universal muffy. Well here a month ago I noticed black stuff that looks like soot on my rear bumper so I had someone run behind me and it appears that when I hit past 6 grand it blows this bllack stuff out. It has new NGK coppers and Acura wires. Any ideas appreciated. shwnoff32@aol.com thanks

 

The only ideas that come to mind is to check you plug gaps and the fuel pressure. Are you running rich? Also a compression check is in order.