After reading this post i went and bought a used Skyline V12+ pipe for my TZ and i have to say i'm not to happy with the seal it makes where the header joins to the pipe. Do you need different types of gaskets or something?
Do your pipes seal ok or are they a little loose? I'm afraid one hit and it will pop out
But i haven't ran it yet so maybe performance might out weigh the fact it's not a perfect fit.