Truth: Most older pellet-type cat converters were very restrictive, but these were virtually all replaced by the mid-80's with new rare metal containing honeycomb type units especially on V8 equipped GM and most other manufactures' vehicles. These new type converters are very efficient as long as they did not become damaged or plugged by lead and other non-converter safe fuel additives. Recent dyno tests have in fact showed that modern converters rob only about 3-8 horsepower depending on application. In many cases, the factory cat-back exhaust system robbed as much as 40 HP compared to an aftermarket, performance-oriented system.  SEE THE DYNO TEST I RAN WITH A CAT AND WITHOUT A CAT ON MY 355 CI V8 HERE

Myth: A catalytic converter holds no real advantage or use on my performance street machine.

Truth: From personal experience, the catalytic converter has been a blessing in disguise for me. After installing the unit(s) first on my 86 Monte Carlo, I immediately noticed how much more smooth the power band was. It seemed as though I had extra low end power without it affecting the top end grunt of my EFI 355 engine. I also noticed a dramatic drop in exhaust odor and sound levels that actually benefited the pleasure of weekend road trips, not to mention the less attention my vehicle attracted from local law enforcement agencies. As an added bonus, I soon realized that I was having to clean my rear bumper cover less often due to the lack of emissions emitting from my tailpipes. (the car was white so you can imagine the black spots right above the tail pipes)

Myth: Catalytic converters are expensive and cannot legally be replaced on my vehicle.

Truth: Modern replacement cat converters range in price of $50 - $300 depending on size and application. If you own a vehicle originally equipped with a converter, the national law states that converter can be replaced after 50,000 original miles.

I will be honest with you, if you own a pre-74 domestic vehicle, chances are it did not require a converter unless otherwise stated by state law. I personally would not put a converter on one of these vehicles due to the cost and confines of space unless I had the parts readily available. Besides it is not required by law unless a modern engine is installed in the vehicle in which case the emissions equipment that came with that engine must stay with it.

So, what does this all mean to you? Well it is up to you, of course, but it is not worth the time it takes to remove and destroy or replace that cat on your 88 IROC with a pipe. I have seen many cases where the shadetree mechanic has tried to weld a 2.5" straight pipe in place of a factory 3" converter resulting in no performance gains but louder exhaust.

It all comes down to how professional you want your car to perform and look to others. There is nothing like racing someone's mid-60's muscle car or late-80's NOS Mustang with headers and turndowns and blowing their doors off with your totally emissions legal daily driver.