I'm currently running an F4i header with an F4 Hindle midpipe and slipon on my '00 F4. The F4i header mounts just fine to the F4 block but as mentioned, it's about 3 inches shorter and doesn't really have much of a bendto it. I took both headers to a muffler shop and hand them make me a 3" pipe to match the bend of theF4 header for $20. I'm guessing if I could get an F4i midpipe, I could do away with the 3" custompice ofpipe.