About 6 years ago when I started testing the HP gains by removing / replacing cats, I found that the biggest restriction for producing HP was the stock cats 4 substrate design.
With a high flowing, lower cell number per inch (more open design) two substrate ceramic cat, we could get within 1-2 HP of a pipece of straight pipe on a 450-500 HP engine.
For years, we carried these ceramic cats.
At the SEMA show in 2004, our rep at the cat manufacturer dsiplay booth told us that we could start getting the meatllic substrate cats that they make for other companies. One of those other companies happens to be Random Tech.
Since we knew that the ceramic cats would get us to within 1-2 HP of a straight pipe and the metallic were a known higher flowing design used by other companies selling Viper cats, we started carrying them without testing for the HP change.
The matallic ones are a single substrate bullet design, where the earlier ones we used were a larger diameter body design.
In either case, the cat change will allow the engine to flow more air and make more HP, and that's the goal for most people. The side benefits are improved sound and cooler side sills.
Since 2000, we've sold at least 500+ sets of cats. We've always supplied a 5 year 50,000 mile warranty with them. Of the cats sold, we've probably warranty replaced 3 car sets. Not bad odds, considering that all those were ceramics and not the tougher metallic substrates.
In regard to emissions, a typical two substrate high flow ceramic cat will usually be able to burn off more excess fuel than a single substrate metallic cat, primarily due to the surface area.
Expect a good high flow cat to pick you up 14-17 RWHP on a 1992-1999 model Viper and 9-12 RWHP on a 2000-2002. 2003+ can see 17-20 by removing the two stock cats and replacing with one single high flow. Those are the average results we see with our chassis dyno.
Below is a picture of one of our direct fit 2.5" cats. They're designed to slip into the stock muffler like the stock cat does. The body is stainless steel. We TIG weld 304 stainless pipe, set to the correct diameter and length, so it's a direct replacement to the stock cat. With this kit, we include two stainless steel strap style exhaust calmps, like the factory uses.
Regards,
Sean