I'm throwing out ideas for my exhaust plans.
Fast intentions high flow cats resonated, don't know how raspy it will be with the non resonated.
Then my diy 2.5" catback with a X pipe with Magnaflow mufflers.

 

With a DIY system watch out for drone and rasp. Manufacturers often put in a lot of R&D to help reduce these 2 annoying conditions in their systems and if you go your own route it's just a crapshoot. Stay with all the pipe diameters the same if you can this will definitely help. You didn't mention coupe or sedan but both utilize a y-pipe, not an x-pipe. And x can be done if you're going true dual but you'll have challenges with the mounting points since both cars stock utilize one muffler with resonators in the mid pipes.

Definitely let us know how it goes, I'm always curious how these DIY projects turn out. Great choices on the FI pipes and Magnaflow mufflers, hard to go wrong with either company so I'd say you're off to a good start.

 

Manufactures like Magnaflow spend hundreds of hours testing their exhaust systems for flow and sound! They do make quality systems, I suggest you buy one from them! Then you can include those FI HFCs and you'll have a cool sound without rasp that will last (almost) forever.
Gary

 

I'm all about saving money by doing stuff on your own; at the end of the day it's the best way to learn. However with exhausts, it's best to just buy something you know already works rather than wasting money and time. I have been running test pipes and muffler delete for over a year now, and even tho I love how it sounds, it is simply too loud and drone-y for a daily. I'm going to be throwing on a Nismo muffler soon to cut down on the drone and actual decibel level of the exhaust. Do it right the first time. Find an exhaust you like, keep an eye out for a used system or just save and buy one new.

 

I've been researching different exhaust systems. The only resource of sound is YouTube, which is terrible. Most exhaust system for the g35 seem too quite or ricy, too raspy, via YouTube. A few didn't. Some not necessarily home built but pieced together and these two systems. I am growing fond of fast intentions and motordyne. Fast Intentions will take 12 to 14 weeks to build, he only wants $300 down for the exhaust and $100 for the hfc and I can pay on it as they build it. Motordyne because it's 2.5" and it sounds mean. They are both expensive but motordyne is ridiculously high. The shockwave is for the coupe but I have to buy two $130 extensions for a sedan if I understand that right. I'm trying to figure out which Y pipe the shockwave comes with? I know they are interchangeable.