I have a cat back exhaust and straight through test pipe and have a tune scheduled for next week. My question is, will i need to get another tune after putting on a downpipe? or will the new one work?

 

Are you already driving with the exhaust parts on the car? Or were you going to install before he tune? If you can wait for everything to be on the vehicle when you tune it would be most accurate result. Not sure when you were planning on getting a downpipe put on.

 

You should tune with downpipe on. The 3 inch downpipe is going to affect boost and air fuel ratio. Also a 3 inch down pipe will net you alot more power then a stock. So tune it with all the mods on.