i just finish putting on my turbo, i check everything over, i pull the spark
plugs wires out and start the car a couple times. when i started it up,
it idles really rough, it feels like its going to die. the VAC guage reads
at 10 but not perfectly. the check engine light is on. theres no exhaust
connected to the downpipe yet. its hard to rev pass 3k.

Is this normal for the car to idle like that on a base map or another problem like the o2 sensor?