I currently have the following setup on my 08 G35X sedan:

FI RHFC, mated to a Topspeed Y pipe and OEM resonator pipe and mufflers.

Also have Topspeed catback which came on the car (currently in the house). Swapped it for OEM because I wanted a it quieter. But I learned that the HFC with the stock exhaust doesn’t sound great, coupled with the fact that it’s still loud and keeps getting louder as the used OEM exhaust starts to rust/leak. If it was just the leak I’d have it welded, but once I’m going for new cats Maybe I should swap this too.

So I’m now looking to go fully stock or just quiet it down.

My questions are:

1) any quiet sounding HFC’s? (I doubt it)

2) what would I need to order to make the OEM style cats mate to the Topspeed Y pipe? Gasket and flange? Should I ask Topspeed about this? Will it work? Should I buy an OEM size Y pipe?

3) best place to buy these parts? Rockauto?

Thanks for any and all help.