My flange between the oem axle backs and mid-pipes are rotted, so both need to be replaced.

Megan racing say their mid-pipes won't work for awd models. What do I need to make them work? Is there a y-pipe needed also to make the install work? If the Megan system won't work, what are my options?

I want a performance stainless system and like the stock style quad tailpipes that Megan offers, but will switch to dual tailpipes if I have too.

IIRC, I used a G35x mid-pipe on my car initially with OEM mufflers (07 M35x at the time), so you should be able to pair your muffler to that if it fits a G35x...but perhaps I'm visualizing it incorrectly not seeing as I haven't had a Y50 in like 5 years.