Friend wants the car out asap and I just have Long tubes and no y pipe. Will it be fire hazard or something? He lives about 10 miles from my house. I dont care about the fumes I will have the windows down lol.

 

The only issue besides sound is if the O2 sensors will function well enough to provide decent fueling on your short trip. More than likely, you will be ok. People seem to get around the dragstrip with open headers ok.

 

Depends on the cops.

 

I'm wondering:
If he unplugs the O2 sensors, wouldn't the PCM default to speed-density mode and then there won't be any worry about strange O2 values from open headers causing extremely high fueling rates?

 

Good idea, wrong logic - Unplugging the O2 sensors does not make it default to speed-density. The MAF sensor would still be working fine. And speed-density does not eliminate the use of the O2 sensors.

What unplugging the O2 sensors it would do is keep it in open loop, and that would prevent the O2 sensors from altering the A/F ratio. As long as the tune is decent, it will be OK.