Newbie question! Downpipe = Overboost?

[KusKus]

So I'm kinda new the whole downpipe upgrades and all since I was planning on putting on a downpipe to delete my secondary cats. I'm just wondering if it would do any problems to my stinger if I put a downpipe and remove the secondary cats but keep my primary cats without any tune? I've been seeing a lot of posts about overboost and all so I just want to stay on the safe side of things since I only plan to make my stinger sound good and daily at the same time.

 

[General_Vodka]

downpipes = primary cats. mids = secondary cats. mids won't cause overboost by themselves. Downpipes might.

 

[Michael Polito]

On my 335i a few years ago I put a catless dp and removed the mids/secondary and I had to do a custom tune on the Cobb due to over boost. PTF did the custom tune for me and it was fine afterwards.
would suck prior to cause it would go into limp mode so I would have to clear all codes and switch the off the shelf tune back to stock and it would be ok.

 

[Oryan]

Midpipes(Secondary cat delete) Shouldn't cause overboost issues by themselves. Primary downpipes may, by themselves and almost certainly will if you open up the rest of the exhaust. Mids can start running into overboost issues as you mod more. Before I got my JB4, once it cooled off the boost hit so hard and fast the car would overboost to the point it would sometimes throw CELs and go into limp mode.

 

[General_Vodka]

When I overboosted there was no CEL. Just no boost. Turning the car off fixed it.