I just got my car back and for about 100mi I haad a CEL, my dad told me not to worry about it, and that the car was just getting used to the new exhaust system we put on, well today i was looking around my fpr and I noticed the Vac line to the manifold was broke. I dont have a CEL, and I would like to konw exactally what that vac line dose and if dirving with it like that hurt it at all?

Basic rule of thumb, if it is supposed to be hooked up, then hook it up.

The vacuum line will apply engine vacuum to the fpr to change the fuel pressure based on engine speed and load.

you can get a CEL when you change an exhaust and cat because of the oils inside the piping burning off and fouling the O2 sensor

thanks man, so my engine wasnt getting the right amount of fuel? I just would like to know if that damaged my engine, I drove around wtih that hose disconnected for probally quite some time, also will I notice any difference in performance with that hose plugged in now, or any change in mpg? Thanks again

When you floor it, the FP goes up maybe 10psi to adjust for the load/engine speed.

I'm sure your car is perfectly fine now although it should feel BETTER with the FP regulator plugged in :P