If your car only has two cats then the H-pipe is aftermarket. Like Stefan said the stock H-pipe will have 6 cats, not 4. Take the car to a muffler shop or a couple of them and have the cats checked out. Most places will do it for free. Your dealer is obviously a joke. Exhaust will still come out even if your cats are clogged. What you could do is gut the cats and get the MIL eliminators. You get rid of the emissions code and get an off-road H-pipe. To clear the check engine light you need to disconnect the battery for at least 30 minutes. Then reconnect and let the car idle for about 10 minutes. Then drive it. Have you looked at and checked your O2 sensors? How many miles are on the car? With the high flow cats that are most likely on the aftermarket pipe I wouldn't think that the check engine light would be triggered. If the cats and O2 sensors are ok then go get some MIL eliminators.
Have you had a computer scan done to see if it is for sure the emissions that is throwing the check engine light? Something else maybe throwing a code if it's not the exhaust/emissions.
Have the cats checked at some muffler shops. If it's not the cats, get the computer scanned to see what the problem is. It'll tell you if it's the O2 sensors or whatever it is that's the problem.
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1994 Red SVT Lightning #2019
[This message has been edited by 96GTS (edited 04-19-2001).]