i dont know if im typing the right stuff in searching or what but i cant find anything on the differences of the lim's. im wonderin on both turbo and n/a btw. any help or direction to where i can find info would help.

 

turbo:

s4 USDM has the EGR casting on the rear runner.
s4 JDM has the brake booster nipple on the rear runner and no EGR.
s5 USDM has neither, and the runners are slightly further spaced apart, and slightly larger in diameter.
s5 JDM has the brake booster nipple on the rear runner, and the above.

I dont think any of the JDM's had the subzero assist valve present, and mid 90/91 USDM didn't either.

For the NA:

s4 and s5 have the same runners spaced the same way, however the s5's flange is about 1/4" wider on one side and the last stud is relocated as well. There are a couple of minor differences as to how the vacuum nipples are routed on s5 as well, but nothing significant. I believe the s5 has the port air passage under the primary runners while the s4 does not.

/thread.