I have a 3inch down pipe made by ar design for my R56 that I am waiting to install but I am wondering if I would have to buy an access port and get it dynoed. Or am I able to bolt it on and go. I'm sure but not positive that I will have to get it dynoed and get a set tune for my car. Feedback please.

 

Are you running the rest of the exhaust stock or do you have a performance system? Is it catless or catted?

If you are running a catless downpipe with a stock exhaust you will see gains but not as much as you could be because the flow hits a lot of turbulence getting crammed into the stock exhaust diameter and hitting the cats. Also I'm pretty sure access port tunes don't remove the CEL you'll probably get running catless or high flow catted though I could be wrong.\

Either way you should tune the car if you put in a performance downpipe to get the max potential out of it.