[Onyx Dragon]

Ok, so I'm still trying to learn engine codes, etc for these cars, so if I get this wrong, I apologize! I have a 1998 328i, and if I'm not mistaken, I have an M52B28, and the 325i has an M52B25 engine. I've heard the intake manifolds on the M52B25 are better, and less choked off. I am thinking of doing this swap and would like to know what all is involved in this. I have searched, but it came up with a lot of links that didn't do much for me (and it could also be I suck at searching). I think I read that there is a conversion kit to do this? Thanks!

 

[witeshark]

I'm not surprised. Just don't rush it.

 

[North]

The 325i's engine is the M50B25, and you're right that the M50 manifold is more free-flowing than the M52 manifold.

A DIY writeup:
Modifications

Link explaining the M50 manifold swap and links to two more DIY articles:
Official M50 Manifold Swap Thread - Bimmerforums - The Ultimate BMW Forum