Our cars have exhaust manifolds stock, right?

 

yes in a simple answer

getting more complex, i believe in the late 80's, performance options were starting and you could get your dealer to install headers and such (on a select few firehawks and irocs i thought)

also, starting in 2000 i think, both f-bodies started getting tubular exhaust manifolds, which compared to shorty headers

 

Excellent. Thanks for the response!