I just bought a 1990 Integra LS. It has 100,600 miles on it. He just changed the exhaust from just behind the resonator. I noticed when I test drove it that it idled alittle rough but thought nothing of it. I already replaced the Pluggs, wires, cap, and the rotor. I've noticed after I changed the pluggs that #1 gets covered in black crap and I've been cleaning it every day or so. Any ideas?