It will probably have a bit of an effect on your car's performance. I'm assuming the conquest is a turbo model? Not sure. IF it is NA it shouldn't be too much worse but if it's turbo then it will be more significant. The thing about catalytic converters is that what makes them work is precious metals, ie: gold, platinum. The chemical reaction that the precious metals have with the carbon monoxide and other carbon based particles in the exhaust cause the carbon to bond to the cat's surface as well as introducing oxygen to make more CO into CO2, carbon dioxide. Some of the top race series in Japan require cars to run cats. Some of the top cat's will have very high precious metal make up therefore they can run fewer "cells". A typical OEM cat will have 300-500 cells making them very small and more restrictive. An aftermarket cat w/ high levels of precious metal will have 30-50 cells making the cells much larger and therefore more efficient at letting exhaust gas through while at the same time cleaning the exhaust as well or better than oem. The only drawback to a good aftermarket cat is the $$$, obviously gold and platinum are not cheap. That's why a crusty old catalytic converter from a junk car that's going to be crushed will still fetch $45-60. Sorry about the length and I hope I enlightened you a bit. I'm trying to remember all of this off the top of my head so a few of my numerical examples may be off by a bit but they are pretty close. Anyway there you have it, hope it helps.