Back in the early '90's, I used to use Random Technologies Stainless high flow cats.
http://www.randomtechnology.com/Catalytic%20Converter%20Installation%20Instructions.htm
Super High Flow Catalytic Converters
Installation Guidelines
IMPORTANT
sFor optimum performance, the converter must be installed so exhaust flows through it in the proper direction. When laying beneath the vehicle with your feet towards the rear, the converter should be installed so the numbers stamped into it are readable.
s Random Technology Super Flow catalytic converters are designed to fit a variety of vehicles. Special adapters may be required or special air tube adapters may be required.
s If a converter with air tubes is installed on a vehicle not equipped with an air management system, both air tube fittings must be plugged.
s If a converter is installed on a vehicle with an air management system, one air tube elbow & one plug must be used.
Plug Installation
Determine which air tube fittings (if either) are to be used to make air connection in your application. (Plug the side away from the vehicle's air supply management system.) Plug the fitting(s) not used before installing converter.
1. As in Figure 1, place converter on a secure surface with air tube fittings up, being careful not to crush the converter body or heat shield.
2. Place plug(s) into airtube fitting(s). See Figure 2 for direction of plug.
3. With a hammer tap plug(s) into airtube fitting (s) until seated. The top of the plug(s) will be flush with the end(s) of the tube. See
Figure 3.
4. Crimp the end of the tube over the plug with pliers. Crimp in at least 4 places. See Figure 4.
Airtube Elbow Installation
The airtube elbow is installed on the same side of the converter as the
vehicle's air supply management system. The remaining tube should be plugged (See above). If your vehicle is not equipped with an air management system, both tubes should have been plugged.
After installing catalytic converter on the vehicle:
1. As shown in Figure 1, insert the airtube elbow into the converter's airtube fitting.
2. Position elbow in correct direction to connect air management system and secure either by welding or by using a small clamp.
3. Complete connection to the vehicle's air management system. (An airtube attachment kit may be required.)
Important Notice
To any person engaged in the business of repairing, servicing, selling, leasing or trading motor vehicles or motor vehicle engines, or who operates a fleet of motor vehicles.
Aftermarket converters may be installed in the following situations.
1. If the vehicle is missing a converter;
2. If a state or local inspection program has determined the existing converter has been lead-poisoned or damaged or otherwise needs replacement;
3. If the vehicle is more than five (5) years old or has more than 50,000 miles and a legitimate need for replacement has been established and documented. (This situation
normally would include only plugged converters or those damaged to the point where unrepairable exhaust leaks are present.)
Note: In order to establish and document that the circumstances permitting replacement of an original or missing converter with an aftermarket converter, the installer must include the customer's name, complete address, and the make, model year and mileage of the vehicle on the service invoice along with a stated reason for replacement. (Where a state or local government has determined that a converter is damaged or needs replacement, the service or repair facility also should retain a copy of the written statement or order by a proper government representative which indicates that the converter should be replaced and attach it to the invoice.)
Where the replacement need has not been verified by a proper state or local government representative, the customer and a representative of the service or repair facility must sign a statement verifying that replacement is justified
This statement form, which is supplied below, must be attached to the invoice and retained by the installer for six (6) months, and the replaced converter (if any) for at least 15 days from the date of installation.
Catalytic converters are emission control devices which are designed to last the life of the vehicle and do not normally require replacement. Furthermore, if the vehicle is properly used and maintained, original converters are covered by the emissions control warranty for five (5) years or 50,000 miles. Federal law prohibits repair businesses from replacing these devices except under certain limited circumstances.
Important
In order for the installation of an aftermarket converter not to be considered a violation of section 203(a) (3) of the Clean Air Act, the converter must also:
1. Be installed only in situations as defined in the three situations above;
2. Be in the same location as the original converter;
3. Be the same type of converter as the original converter (i.e., oxidation, 3-way plus oxidation);
4. Be the proper converter for the vehicle application as determined and specified in the aftermarket catalytic converter application guide;
5. Be connected properly to any existing air injection components on the vehicle;
6. Be installed with all the other required converters for the particular application if more than one converter was specified in the aftermarket catalytic converter application guide;
7. Be accompanied by the warranty information card, filled in by the installer. (Warranty Card is included in converter package.)
