Black R

Hi guys,

I'd like to go from my current 3" downpipe to a 4", but my engine swap has this exiting on the passenger side (usdm).

There isn't much ground clearance right now as the exhaust has to cross under the frame rail to exit in the stock location.

Now in the future I'll be lowering the car another 1" and also going with the bigger downpipe.

My idea is to go with a 4" y into smaller duals (2.5"?)
I want to make sure that the sizing of the duals flows at least as much, if not more than the single 4" pipe.

I've scoured burns site, as well as google, just looking for the proper volume of duals compared to a 4". I could get anywhere from 2" to 2.5".

Thoughts?