I’ve been looking at the Invidia Q300 for my IS250 for some time now. But the damn thing just hovers around $600 and never drops, until I found, essentially, the same one for $471 but it says it’s for the GS 350. From the picture, the two parts look identical. I kind of tried searching into it myself but I can’t quite find an answer to this particular question. So do they share the same axle back set up? If not, are they close enough to get away with using the GS axle back on the IS?

 

Not without modifications, the RC models are a direct bolt on for our 3rd gen IS rwd

 

This.

Also, checkout the marketplace:

https://www.clublexus.com/forums/market/

 

Is that not the case for AWD even if it’s just an axleback exhaust?

 

RC and IS are the same axelback.. not the GS.