I have a 1990 Pontiac firebird and I have no idea about what to buy for a true dual exhaust. The car has a 305 engine and I have no idea if that is relevant 😂

 

There are a few threads on here about dual exhaust. Since these cars sit pretty low, clearance can be a problem. Most of us use shorty headers into a Y pipe that follows the factory path to the muffler with dual outlets. True dual is usually long tube headers with dual mufflers. some exit to the side and some go straight out the back. If you are in a state that requires inspections, you'll need dual high flow cats. Don't forget the O2 sensor. Most headers have the bung already welded on but you have to drill and tap it to install the sensor. It's a good opportunity to install a heated sensor. Do a search on here for dual exhaust and you'll find more detailed info and probably some pics.

 

There is also a sticky about this topic.....
https://www.thirdgen.org/forums/exha...l-exhaust.html