Was 90% set on ordering an FI system, but thought I'd check a local performance shop for options. The owner of the shop I visited told me, he'd install any cat back system I could order for $125.
He also had a couple of full system, can't remember the names for about $1,250 installed. Then asked me if there were any other mods I was planning or entering a car show, I replied no.
He then proceeded to tell me that the biggest clog in the exhaust system in the Z after the cats is the stock muffler. Then offered me to remove the stock exhaust, install 2 glass packs, straight inline with the existing pipes to the tips. I also wanted to keep the stock tips which he did. The price he quoted me was $400 total.
I figured, it was worth the risk. If I didn't like it I wasted $400 but I could still order the FI. I have got to say, almost 3 years after installing, I am so happy that I made that decision. Saved me $1,500, sounds great, no drone, butt dyno immediately told me increased performance, almost 2 miles more per gallon and it looks great.
As some has mentioned, it maybe worth checking out some custom options that are much less expensive.