In keeping with the "You get what you pay for" scheme, a cat-back exhaust system is the best exhaust upgrade available for the Probes. The cat-back kit is just what its name implies: a complete replacement of everything from the catalytic (cat) converter backward. This includes all piping, and the muffler and tip. These kits are by no means cheap, but offer much larger performance increases than a simple muffler upgrade can. 

Have you ever had the misfortune of seeing your Probe's stock exhaust system?  If not, take a look at mine.  You should notice that the factory pipes are not mandrel bent.  Because of that, there are "pinches" where the pipe is bent to form the curves and/or corners. The effect is that it creates more turbulence and retards the flow of exhaust somewhat.  Most cat-back systems will have mandrel bent pipes to correct this, but it is in your interest to make certain!

You may also notice in that photo that the piping seems to be made of mild steel. The factory piping had a smooth, glossy look and feel to it (on the outside).  I am not sure if this is some kind of protective coating from the factory or if it is just the pipes becoming glazed due to the heat (which is more likely!)  This is a good place to again remind you to certain that the kit comes with piping that is at least aluminized or stainless steel, no mild steel!

Also, cat-back systems generally have larger diameter piping that replaces the factory pipes. Manufacturers spend a lot of time and money on Research & Development for these systems.  You may have read before that piping that is too large in diameter will actually cause a DECREASE in horsepower.  This is true for normally aspirated engines and the trick to these exhaust systems is to have the least restrictive exhaust without overstepping the engine's bounds. Because of this, each system is specifically designed for each model, there are no "generic" cat-back systems!

Finishing off the kit is usually a free-flowing muffler with tip(s).  Most are straight-through designs, however there different techniques are used to arrest thesound.  This photo of the cutaway GReddy muffler shows how the pipe runs straight through the muffler.  Although it is difficult to see, once the pipe enters the muffler it is perforated. Sound is absorbed by the fiberglass batting through the perforations while the exhaust is allowed to flow unobstructed, out of the muffler.  Other mufflers, such as the HKS have straight-through design, but use internal baffles which block some of the exhaust and are most likely responsible for its lower HP rating. The HKS is also one of the most quiet systems available for the Probe.

Unfortunately, the cost of the cat-back exhaust systems is their one downfall. They start at about $300 and can run up to nearly $700.  This puts it them out of reach of all but the diehard performance buffs who are willing to blow some serious cash on them.  Believe me though, they are worth every penny!

Installation cost should not be more than $30 or so*.  These are direct bolt-on replacements for the factory gear and the only labor is to unbolt the old and bolt on the new!  If you are at all mechanically inclined and own a 17mm & 14mm socket and a jack, you could do this yourself.  The most difficult part will be breaking the nuts on the old system.  Moisture and the high heat from the exhaust do a fine job of seizing them up.  This is especially true for the (2) nuts at the converter flange as cats generally function at over 700°F.

*One very important note for 1996 and 1997 Probe owners:

If you have a '96 or '97 Probe and plan to install a cat-back system, note that the installation will NOT be a do-it-yourself job...bring it to a trustworthy shop!

Since the addition of the OBD-II (On-Board Diagnostics) exhaust systems in 1996 and 1997 models, the exhaust systems are slightly longer in the mid-pipe than they are in the '93-'95 models.  Also, the 1996 and 1997 models are different from each other. They appear to be the same overall length, however, the '97 "splits the difference" between the mid-pipe and the muffler length, while the '96 has the difference in the mid-pipe only.

Most cat-back systems were designed on the '93-'94 models and since the same part numbers are normally used for all second generation Probes, chances are that if you purchase a cat-back system for your '96, the mid-pipe will be about 6" too short. For the '97, the mid-pipe will be about 3" too short AND the tip will be recessed under the rear valence about 2"-3".

This is a known problem and there is relatively no cause for alarm.  All that is required to fix this is to have an extension added between resonator and the flange leading to the converter.  If you have spent the money on a kit that utilizes stainless steel piping, INSIST that the extension that will be installed is also stainless.

So, as you may have already guessed, this will probably add to the cost of installation, however only very slightly.

What can I say?  This is, by far, the best choice of exhaust upgrades for your Probe.  Not only will these systems give you more horsepower overall, that horsepower is applied over a wider power-band than just the mufflers.  Depending on which system you choose, increases can range from 10-15+ HP.  That doesn't sound like that much more than the mufflers, BUT that power is available over a wider power-band.  Unlike the muffler with 8-11 HP at only ~4500 rpms and up, the cat-back systems will give 10-15 HP from ~3500 rpms on up.  There is a huge difference.  

Cat-back systems generally give the most "refined" sound.  None of them are harsh and for the most part, they do not drone.  Most are even more quite than the either the universal or performance mufflers under normal driving conditions; however, hard acceleration will have them screaming fairly loudly.

Cat back systems usually end with a very eye-pleasing muffler and tip. Most have highly polished stainless steel mufflers and tips that really call attention to themselves.  The GReddy tip is just over 5" in diameter and the HKS is about 4.5". These give the car a more aggressive look.  The Borla Cat-back is different and ends with dual intercooled tips.  

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