UIM Differences
 

Im currently running a S4 tII motor with S4 tII intakes. I came across a FD LIM, UIM and TB off a A/T FD. It looks like the center ports where the two intakes meet are smaller. I know i would need an adapter to use the FD UIM onto my S4 LIM. Does the FD one actually flow more than the FC?

Use the S4 lower and port to match search you'll find info