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?

Please Help or point me in the right direction

 

Try resetting the ECU. Then start up the car and let it idle for 15 min to allow the ECU adjust to the new mod. Also do not touch the throttle while car is idling.

 

How do I reset the ECU.

 

I checked the ECU and it doesn't show any problems. I believe the problem to be with number 1 fuel injector but what can I do to prove it before I buy a new injector for $100.00?????