Swap Questions

[Viper3812]

I have a few questions for my upcoming swap.

What diff do you guys have or reccomend? Is A 3:45 a good choice?

I already have bavauto springs and bilstein sports, so do I need to change my front springs and struts to 325 springs and struts or will I be fine?

What exhaust setups are you guys using? All custom or did you buy a cat-back and cut it? I was thinking of whatever header I can get a hold of, AA trackpipe then idk what for the cat-back (AA Gen 3 cat-back modified)?

Do we need to get the 6 cylinder expansion tank for cooling? If so, where did you guys mount it?

Thanks.

[1996 328ti]

I know this has all been discussed.
A 3.45 is fine. You are going to rev almost 4K at 80 mph.
I'd install a diff made for a 6 cylinder.
I have twin cats that are fitted into a Y pipe to a single exhaust
I think it's a Dynamax or Dynaflow.
I had 323ti sport springs.

Replace the radiator and motormounts.
Will you have and CEL issues? I did.