Hello Guys, I have a 91 si with a zc swap sohc. I bought this car for around 500. The Car had a real bad vacuum leak coming from the brake booster. I changed the brake booster. Then I added some headers,and a cold air intake. Started it up and NOw its running terrible. Worse than before. The Car backfires everytime you push the accelerator. The motor is vibrating real bad as well. Any Ideas ?

 

Go back and recheck all the basics... O2 sensor, Spark plugs, ignition wires, timing, IACV plugged in, reset the ECU.