On Fri, 10 Nov 2000, Rob Hook wrote: > In most states a car with a missing catalytic converter could have > passed up until a few years ago, assuming the inspector didn't > physically look for a catalytic converter. That's really no longer It really varies from place to place. In Colorado, 1981 and older vehicles get a *much* less thorough emissions test than more recent cars. Most (if not all) states have some sort of age-related emissions exemption - although just how old your car has to be, and what sort of a break you get, varies from place to place. On any car, simply replacing the catalytic converter with a piece of pipe may or may not improve acceleration and will surely make it louder. It is possible to make specially designed pipes which improve power with minimal increase in noise, but I don't know of any available for the DeLorean. The best solution, unless you have a good reason to do otherwise, is simply to leave the original cat in place. The DeLorean exhaust and manifold are restrictive enough that the cat is not a major obstruction by itself. If you are planning on extensive exhaust reworking you might get some benefit by removing the cat - but replacing it with a modern cat will yield better-than-stock emissions and only 1 or 2 HP difference in power vs. a straight through pipe.