Keep the catalytic converter and EGR. Modern high flow converters are very efficient and can be found for less than $100. Ash can the old school myth of smaller exhaust pipes retaining torque at lower RPMs. Anything beyond the exhaust manifold exit or header collector will add very little torque. Too small an exhaust will kill any chance of gaining any torque throughout the RPM band once you start increasing airflow through an engine. The stock computer can compensate for small changes in airflow/efficiency due to better intakes, mild cams, exhaust, headers etc. Going too far outside it's design parameters will result in poor performance and possible engine damage.

Changing the exhaust to flow better air is an excellent way to improve mileage and performance. As noted before the Feds frown upon changing emission components unless the originals are faulty. In your case, the catalytic converter has been violated. Mine was the same way on my '92 F350. Completely hollow from the previous owner. The entire exhaust was rusted out and falling apart. I replaced everything including the manifolds.

I have posted before my combination on my 5.8L:

Dorman replacement manifolds (cheap until I want to spend more $$)
Bassani 58150B2 SS y-pipe ( designed for a Bronco w/5.8L)
Magnaflow Spun Series Catalytic converter p/n 59929
Magnaflow 3" In/Out Center/Center SS muffler 12279
Dynomax/Walker 45683 3" aluminized steel mandrel bent w/two hangers attached ( designed for a mid-90's Chevy truck)
Dynomax 3" SS band clamps 33272

Now I have a very free flowing mandrel bent 3" exhaust. All the parts, including manifolds, were ~$600. I installed it all in my home garage without a welder. The muffler has a 24" body so even though it is a straight through design, it is quiet with a deep rumble. I also took the opportunity to replace the missing EGR tube to make the EGR functional again. There are several manufacturers who make emission friendly headers for our trucks at a reasonable price. Keep the cat and EGR. Once you replace your old cat with a modern 3-way you can ditch the air tube system, keep the relays connected to make the computer happy. We all have to breath this air, try to keep it as clean as possible.

 

I have an 86 f-250 351 carb'd there is no catalytic converter, and I do not believe it came with one. Is there any way to prove this to the NJ DMV?

 

Check the underhood emissions certification sticker, see if it says catalyst on it.

 

Bingo! Although I have read some inspectors still swear there should be a converter in place.

 

Thanks for the so fast response, If it wasn't so bloody freezing here in NJ I would be outside checking now.

 

10-4 It is a non-catalyst.. Thanks again!!

 

I have been researching installing a straight exhaust system without the cat. Some folks told me that removing the cat from the system will not throw a code. Has anyone on here converted to just a straight exhaust system without a cat?

 

Walker Y-pipe and converter. $165 on RockAuto. More Information for WALKER 15739

Staying legal and compliant is inexpensive. My truck ran better with a new converter, I think the old one was clogged after 20 years.

 

Unless you are in California and your catalytic converter is $400

 

Then you wouldn't get away with removing it anyway...

 

I removed my EGR on my 89 351w and lost a half MPG, and later added shorty headers and gained 1 MPG average. So if you remove your EGR and add headers, it'll probably be a wash in MPGs but the power and responsiveness of the engine is a benefit I wouldn't pass up.

If you remove the catalytic converter and run without a muffler it's going to be loud. I cut mine off my truck when I got it (it was plugged and glowed red and we don't have any inspections here). It won't throw a code but it's a hefty fine if you get caught without it.

 

I am guessing you have since fixed what the PO didn't causing the cat to melt down. It was trying to clean up the rich mixture. I would bet that once you fixed the engine issue you could have replace the cat and not had any more issues with it.

I don't understand why so many people remove the cat. Performance converters do not cause performance issues on a stock or even mild performance engine and even if the state didn't have inspections it is still against federal law to remove it. Over on a Jeep forum those guy in Kalifornia are scurrying around trying to find 30 year old emissions part so they can pass visual inspection. No way I would live out there.

 

It's not just a visual inspection, it's actual "sniffing the tailpipe" on a road simulator dyno that we have to pass. The bad part is most of our mechanics have no clue what they're looking at. A good number of smog techs weren't even born when the 1976 model year vehicles were built.

Here in "The Peoples Republic Of Kalifornistan", I have issues with smogging my truck, being reight on the borderline each time. I'm guessing 1997 OBS 7.5L trucks with Kail OBD-II were a rare bird, since my truck is a Federal Emissions OBD-I variant, first owned by the State of Nevada. The correct bolt-on Cat can't be purchased here in Kali and the aftermarket one with an Air Resources Board EO number, a Magnaflow part, actually isn't a true bolt-on (clamp on?). And technically, by using that Magnaflow Cat, not the OEM one, I'm "modifying' my emissions system.

When I retire, I'm headed to Indiana. I've had enough with this tree-hugger communist state.

 

Is it really that bad? I smogged my 97 yesterday, with a brand new Magnaflow cat, and had absolutely no problems with visual inspection.