(e39 540 1999) best size for perfomance

[warren_540]

1999 540i auto w/ cold air intake

I been scratching my head all day long because i can't find what i'm looking for. Maybe someone can help me.

What's the best size for performance on a muffler.

could i go 3" to dual 2.5" muffler tip
could i go 2.5" to dual 3" muffler tip
could i go 3" to dual 3" muffler tip

or what would you suggest for best performance?


thank you in advance
Warren

p.s. Is Magnaflow any good?