300ZX Exhaust

300ZX Exhaust<

On a non-turbo Z, one of the best set-ups is a high quality muffler combined with a 2.25-2.5" pipe coming from the catalytic converter.
For turbos, get the biggest exhaust and muffler you can find. You should also consider not using a muffler, if you leave the converter intact your car will not be unacceptably loud without a muffler, turbos are excellent sound absorbers.

Complete "cat back" systems are available of course. Just take off the old pipe at the converter, and put the new system on. Quality, performance, and price vary considerably between brands:

Certified Muffler makes 3 inch downpipes and 3 inch cat-back exhausts. Many options, stainless or mild steel, etc, etc. Their web site with detailed pricing is here. The 3 inch downpipe is highly reccomended. Yes the downpipes are only for turbos. The cat-back stuff fits any 2 seater(Dunno if they have 4 seater cat-backs), and all the parts can be fitted individually to stock exhausts. (ie. you can get just the down pipe, or whatever and it bolts right on).
Custom exhausts are as good or better than any aftermarket exhaust system you can buy assuming it is competently made. Expect to pay up to $100 to have a quality exhaust system custom fitted to your car from the converter rearwards with you supplying the muffler(Significantly more for stainless piping). Some localities will be considerably more expensive, and a quality muffler will range anywhere from $40 up to $200 for fancy stainless steel units. If your local muffler shop says that 3 inch pipe won't fit, kick them in the jimmy and go to a different place. It will fit fine despite what they say. It would be advisable to shield your differential from the exhaust if you have a LSD with either the factory metal heat shields or, if your exhaust is too large for the factory shields to fit, either custom made shields or heat tape available at any respectable speed shop.
HKS will run you approximately $300 but is a very high quality kit. Highly reccomended if you can afford it for a non turbo, or a basically stock turbo. It is insufficient for a highly modified turbo though, but with the stock turbo it's more than adequate.
Dynomax will run you around $140 or so, good quality, but comes with an asthmatic muffler. Not reccomended for modified turbo cars.
Monza is fairly low quality and price, about $100. Better performance than stock but leaves lots of room for improvement. Reccomended for stock replacement on cars where performance is not the most critical concern.

Headers, naturally, are also available. Header information will be added soon, until then ask for opinions on the message board.