I want to eventually redo the whole system with exhaust and headers and converters. Can i go tiwht a cat back exhaust and install it and then add high flow cats after, then add headers later? Does it make sense I do not want to spend all the $$ at once so want to know if i can split it up.

 

Depends on what's most important to you, gains in power or gains in volume.

The G's OEM rear-section seems to flow pretty good, yet the cats are pretty restrictive, with the headers and Y-pipe next in line.

Personally, I plan on keeping the OEM rear-section in place for good. That being the case, I'll install the headers, cats, y-pipe and splice a reducer cone onto the OEM rear-section pipe all at the same time, to avoid added installation cost.

I'd suggest having the headers and cats installed at the same time, both to avoid repetitive install costs AND to get the biggest gains at one time. If possible, do the Y-pipe at the same time for the same reasons. The rear-section could easily be saved until last. The cats and headers will increase your exhaust volume as well.

The other option is doing just the rear-section first if you're really looking for just an increase in volume.