it runs rough and when you give it full throttle it sounds really loud through the intake and won't rev past about 3500rpm.
this is on a 91 integra. Its also putting black soot all over the spark plugs.

Could a bad map sensor cause this?

 

Yes. It also sounds maybe like your TPS.

 

my friends nissan did the same thing...he took it to a shop and all they did was replaced the map sensor and it worked great after that

 

yeah code 3 is map sensor...assuming ur using a pr4...replace that biatch!

 

if you can get another map and swap out.

 

I just ran the car for about 10mins and didn't get a code but the thing still won't rev past 3500rpm.
Its also smoking pretty bad and the smoke is white. But there's no bubbles or anything in the coolant.
What about a plugged cat? or messed up timing?

I also tried another map sensor and ecu and no change.

 

Fixed!
Exhaust was plugged.